Deflated Gas Holders

Gas holders, also incorrectly referred to as gasometers - they don't measure anything - were once a common sight in UK towns and cities. They provided a means to store gas, and to maintain the downstream supply at what is called district pressure.

The first gas holder in the UK was erected in 1798, at the Soho Manufactory, in Birmingham. The water-sealed telescopic form, which came to dominate, was invented in 1824, the first constructed in Leeds. The earliest telescopic holders had two lifts, supported by columns. Later models had up to four, frame-guided, lifts. In 1890 William Gadd, of Manchester, invented the spiral-guided gas holder, the helical runners of which obviated the need for an exoskeleton. The last of these was built in 1983.

The gas was stored at near atmospheric pressure, the necessary weight applied by the heavy cap. The tank containing the gas floated in a reservoir of water, which provided the necessary seal, and rose and fell as the volume of stored gas either increased or decreased. A lipped channel around the base of each lift picked up water from the reservoir as the gas holder rose, thus maintaining the seal.

The holders were often sited next to plants producing town gas from coal, but were steadily adapted to store natural gas. Typical volumes for the larger holders, up to 200 feet in diameter, were 1.8 million cubic feet. As a nationwide network of pressurized pipes and regulators for provision of natural gas was developed the holders increasingly became redundant. A few still serve to balance pressure in the pipe network, but in 2013 National Grid announced plans to steadily remove the gas holders of England and Wales. SGN has similar plans for those in Scotland.

The three gas holders visible from the Aston Expressway, Birmingham, were decommissioned between 2009 and 2011. The conjoined pair, erected in 1885, were once part of the Windsor Street Gas Works; sometime in the 1980s they were painted in the claret and blue colours of nearby Aston Villa Football Club. National Grid has been granted permission to demolish all three holders, which are expected to disappear in 2020.

(Second photograph by Abi Smith.)

Foel Ortho

Foel translates from the Welsh as bald, or bare, hill. But the hillside at Foel Ortho is anything but bald.

In a ruinous state at that time, the farmhouse was discovered in 1967 by Jenny and Eddie Matthews.

The steep acre of ground, between Penybontfawr and Lake Vyrnwy, has over the decades been graced with a series of DIY follies.

With winding and stepped paths between fake rocks, stone-retained terraces, a mock castle, towers linked by a bridge, buttressed walls, and a giant chess set, the place is like nothing so much as a miniature Portmeirion.

Freetown Christiania

Christiania, now covering about 19 acres of the military barracks of Bådsmandsstræd (abandoned from 1967), and remnants of the city ramparts, in the Christianshavn area of Copenhagen, was squatted in 1971.

A mission statement was co-authored by the journalist Jacob Ludvigsen: "The objective of Christiania is to create a self-governing society whereby each and every individual holds themselves responsible over the well-being of the entire community. Our society is to be economically self-sustaining and, as such, our aspiration is to be steadfast in our conviction that psychological and physical destitution can be averted."

The residents developed their own set of rules: no stealing, violence, guns, knives, bullet-proof vests, hard drugs, or bikers' colours. Known also as Freetown Christiania, the commune's cannabis trade was largely tolerated by various Danish governments, some of which saw the area as an interesting social experiment.

Since 1994 the residents have paid taxes for services such as water, electricity and rubbish disposal. The area's open but illegal cannabis trade was ended in 2004, after which outside biker gangs vied to take over the market.

A Christiania resident was killed in April 2005 as a consequence of the resulting violence. The weed trade recommenced, and has operated ever since, other than subsequent to a shooting in 2016 and for a while after police raids.

Since 2010 matters have settled somewhat, and Christiania now operates (largely) under Danish law. Some of the buildings, including the Grey Hall riding house (used as a concert venue), the half-timbered Commander's House, and the 17th and 18th century powder magazines, were listed in 2007 by the National Heritage Agency.

The area was closed to the public by the residents in June 2011, but a year later they set up a collective fund to enable purchase of the land from the defence ministry, making the commune the landowners. No private cars are allowed within the commune, which is currently home to about 900 people.

Broen / Bron

The Øresund (Danish) or Öresund (Swedish) Bridge is a four-lane motorway and twin-track railway bridge that links Copenhagen and Malmö. The two-deck bridge at the Swedish end of the crossing is 4.9 miles long, and terminates on the artificial island of Peberholm, from where the 2.5 mile Drogden Tunnel runs to Amager, in Denmark. It is Europe's longest combined road and rail bridge. The tunnel was necessary to prevent interference with the flight path for Copenhagen Airport, and to provide a clear passage for ships and ice floes.

The bridge, the principal engineering design of which was undertaken by Ove Arup, was built by a joint venture between Hochtief (Germany), Skanska (Sweden), Højgaard & Schultz (Denmark), and Monberg & Thorsen (Denmark). Construction commenced in 1995 and was completed in August 1999, three months ahead of schedule, at a cost of c.€4bn. The official dedication took place on 1 July 2000. The bridge weighs in at 81,000 tons. The three cable-stayed sections together total 1,611 feet (a third of a mile) in length, and are slung from concrete towers 669 feet high, providing 187 feet of headroom for shipping. Otherwise the bridge is supported on concrete piers spaced at intervals of 459 feet.

Peberholm - Pepper Islet - so-called to partner the nearby natural Saltholm - is built from Swedish rock and the material dredged during construction of the bridge and, in particular, from the trench in which sits the tunnel. The island is 2.5 miles long and averages a third of a mile wide. On the island the train tracks emerge from the lower deck of the bridge and splay out to parallel the vehicular traffic. The Drogden Tunnel comprises 2.2 miles of immersed tube, in twenty concrete sections of 54,000 tons each, 125 feet wide, the largest in the world, plus approach tunnels of 886 feet each. Five side-by-side tubes accommodate two train lines, two lanes of vehicles in either direction, and services and emergency access.

(Photographs by Abi Smith.)

i360 - World's Most Slender Tower

Brighton's i360 'vertical pier' was conceived and designed by Marks Barfield Architects, the same team that was behind the London Eye, also sponsored by British Airways. It is sited at the landward end of the ruined West Pier. Built at a cost of £46m, the civil and structural engineering undertaken by Jacobs UK, it is Britain's tallest moving observation tower. At 531 feet tall, it mirrors the height of nearby Beachy Head. Aluminium wind-diffusing cladding aids a damping system in addressing the inevitable wind shear.

A significant portion of the structure is underground. 2,000 interlocking concrete piles were sunk about 65 feet into the underlying chalk bedrock to enable excavation for the foundations. Over 7,000 tons of shingle was removed, to a depth of about 20 feet, and the concrete base for the tower - over 4,000 tons of concrete reinforced by about 195 tons of steel rebar - built directly upon the bedrock. A precision-engineered 21.6 ton anchor bolt frame was set into the concrete.

The tower is formed of 17 steel tubes, fabricated in the Netherlands by Hollandia Infra BV - the main contractor. Delivered to the beach by barge, along with a jacking frame nearly 200 feet tall, and the counterweight for the pod, the tubes vary from about 15 to 39 feet in length, the shorter ones at the bottom. Their wall thickness reduces with height, to a minimum of just ¾ inch, giving a thickness to diameter ratio less than that of a can of beans. The first three tubes were lifted into place by crane, and bolted to the anchor frame. Four tubes were lifted into place atop the first three, and bolted together, but not to those beneath. The temporary jacking tower then lifted these four tubes, enabling a fifth to be slid in from below and bolted to those above. The final lift, of 13 conjoined tubes, was of about 965 tons. This 'top-down' method of construction obviated the need for a tower crane. Work commenced on site in July 2014, and was completed in July 2016, but the tower of tubes, joined together by 1,336 bolts, reached its full height in just ten weeks.

The tower is just 12.7 feet in diameter. With a height to diameter ratio of 41:1, it is the most slender in the world. It is all the more remarkable, thus, that the pod, suspended from eight steel ropes, is as large as it is. 59 feet in diameter, and weighing over 92 tons, this can carry up to 200 people. The oblate ellipsoid pod was designed and built by Pomagalski SA, the French cable car specialists, and ascends to 453 feet. It consists of trusses that cantilever off a central chassis. 24 solid floor sections sit atop the trusses, and atop those sit 36 glazed sections, 24 facing outwards, and 12 facing the tower. The double-laminated glass, which can't be cut once toughened, had to be first cut to shape before it was double curved at high temperature. The drive mechanism, housed in the basement, is akin to that of a cable car. The descent produces about half the power needed for the next ascent.

As part of the development the Italianate Victorian tollbooths that used to flank the entrance to the pier were reconstructed. The originals were designed by Eugenius Birch as an integral part of his pier of 1866. The western one had been demolished, and the eastern was structurally unsound. The latter was dismantled and detailed measurements were taken. Ductile cast iron mouldings - 24 tons of them - were made anew, by the Swan Foundry, of Banbury, so as to precisely replicate the originals. The western tollbooth is now the i360's ticket office, whilst the eastern operates as the West Beach Cafe & Bar.

Penang - Kek Lok Si

Covering about 30 acres, and home to millions of representations of Buddha, Kek Lok Si is the largest Buddhist temple in Malaysia.

Built in the main between 1890 and 1905, the temple is still very much under construction. One of the chief patrons was Cheong Fatt Tze, he of Penang's Blue Mansion.

It is a pilgrimage destination for Buddhists from across South East Asia. Two monumental structures provide the key attractions.

The first is the Pagoda of Ten Thousand Buddhas - known also as the Pagoda of Rama VI, the king of Thailand who laid the foundation stone - completed in 1930. 98 feet tall, this houses 10,000 bronze and alabaster statues of Buddha.

The second is the 99 feet tall bronze statue of Kuan Yin, the Taoist goddess of mercy, the tallest in the world, still undergoing the decorative process.

Nearby is a 200 foot long pavilion of three tiers, completed in 2009. Both the latter can be reached by way of a funicular railway from lower tiers of the temple complex.

The temple's eclectic mix of Mahayana (complete enlightenment) Buddhism, Theravada (conservative) Buddhism, and traditional Chinese Taoism - Kek Lok Si Temple translates as Heavenly Temple, which covers all the ground - explains its widespread appeal.

The next planned development is a temple for the reception of Buddha relics. The fund-raising stalls of tat rather belie the Buddhist principle of not holding.

Penang - Curtis Crest Treetop Walk

The Habitat is an area of conserved regrowth rainforest, cut down by the British to enable the building of bungalows in the cooler air atop Penang Hill. Its structural highlight is the Curtis Crest Treetop Walk, which opened to the public on 1 May 2017.

This 360-degree viewing platform, about 330 feet round, stands about 40 feet above the ground from which it springs. At 2,690 feet above sea level, it is the highest point in Penang, and provides a stunning view of both George Town and virgin rainforest.

The structure, which is cantilevered from a series of canted uprights that were designed to resemble chopsticks standing within a bowl, is named after the first superintendent of the Penang Botanical Gardens, Charles Curtis. Perunding YAA, of Penang, provided the structural engineering expertise.

Penang - Goddess of Mercy Temple

Founded in 1728, the Goddess of Mercy Temple, in George Town, Penang, is the island's oldest. It is dedicated to Kuan Yin, the Taoist goddess of mercy, but started life dedicated to Ma Zu, the Hokkien deity of the sea, patron of seafarers.

Its conversion took place in 1824, when the temple was renovated, reflecting the more diverse origins of the Chinese community in the city by that juncture. The temple acted as mediator in disputes between the Hokkien and the Cantonese, run as it was by a balanced committee of the two ethnic groups.

These secular purposes transferred to the Penang Chinese Town Hall subsequent to the Penang Riots of 1867. Remarkably, the temple survived unscathed the aerial bombing that presaged the arrival of the Japanese in December 1941.

The building features extensive porcelain decorations, created in the chien nien style, which involves clipping into the requisite shapes many thousands of pieces from broken-up Chinese bowls of various colours.

Standedge - Longest, Deepest, Highest

The Standedge canal tunnel, on the Huddersfield Narrow Canal, is one of four parallel tunnels - the other three are railway tunnels - that run through the Pennine hills between Marsden, West Yorkshire, and Diggle, Greater Manchester. The Act of Parliament authorising the canal's construction was passed in April 1794. Benjamin Outram, acting as consulting engineer, estimated the total cost, including the tunnel, at £178,478, and the construction period at five years. Nicholas Brown undertook the necessary survey work, which foresaw a tunnel of 5,456 yards.

Outram was appointed site engineer, and Brown surveyor and superintendent. The tunnel was driven from both ends at once and from intermediate shafts. The intermediate workfaces were abandoned in the autumn of 1796. This change, greater water ingress than expected, and difficult geology, slowed progress. The rest of the canal was completed by 1799, and horses used to transship cargo over the Pennines between the completed sections. Tenders for work on the tunnel went unlet, and it was found that the headings had been driven several feet higher from the Diggle end than from the Marsden (above). In 1801 Outram resigned and Brown was dismissed.

In 1806 a new Act of Parliament provided for the raising of further finance. Thomas Telford was consulted, and in 1807 drew up a plan for completion. This corrected for the crooked workings driven from the intermediate headings: the tunnel has noticeable bends. Finally completed in March 1811, and at a cost of £123,803 for the tunnel alone, this was 5,445 yards (3.1 miles) long, 636 feet below ground at its deepest, and 643 feet above sea level. The longest, deepest and highest canal tunnel in the UK.

In 1822 the tunnel was extended 11 yards at the Marsden end, to accommodate reservoir works. In 1893 it was extended again, by 242 yards, this time at the Diggle end, so that the 1894 railway tunnel could be carried over it. These additions supposedly made the tunnel 5,698 yards long, although modern survey techniques make the total length 5,675 yards (3.2 miles).The tunnel has no towpath, which required the canal boats to be legged through. This was tough and dangerous work, not least given that large parts of the tunnel were left unlined, with the native rock jaggedly proud of the ever-changing overall profile. Some sections are lined with rough-dressed stone, and some with brick.

The Huddersfield and Manchester Railway bought the canal in 1846, which enabled the first railway tunnel, completed 1848, to be driven without the need for ventilation or extraction shafts. Drainage adits (above) drain the higher railway tunnels into the canal tunnel, and gantries (below) link the former. When the railway tunnels were driven much strengthening work of the canal tunnel was required in the form of heavy brick arches.

The tunnel officially closed in 1944, when maintenance ceased. Dilapidation prevented all but a couple of later exploratory journeys. A £5m restoration project in the 1990s set about reopening the canal in its entirety. Shotcrete and rock-bolting were used to stabilise some of the unlined sections of the tunnel. This reopened in May 2001, after 57 years of disuse. Boats were tugged through by electric tugs, but since 2009 have been able to transit the tunnel under their own power, with a pilot aboard, and chaperoned by a vehicle driven through the adjoined first railway tunnel (below). The journey takes about two hours.