Dudley Zoo: Save the Tectons

Last month, to the surprise of its regulars, Dudley Zoological Gardens in the West Midlands popped up on a worldwide endangered list. Not because of Sarah, its Sumatran tiger, or its rare Asian lions, its Humboldt penguins or the black lemurs for which it holds the European stud book. DZG, as it is known, was the sole 20th-century British entry on the World Monuments Fund's 2010 Watch List – of world-class buildings threatened by "neglect, demolition or disaster" – for its 12 Thirties pavilions designed by the architect Berthold Lubetkin and his Tecton Group.

"This is the best-surviving collection of Tecton buildings in the world," explains Jon Wright of the Twentieth Century Society, which helped bring the pavilions to the attention of the list committee. "There's nothing else that comes close."

"What buildings?" says 17-year-old James Bissell, from Birmingham, wandering about the zoo on an overcast autumn day with Melissa, a fellow student on the animal care course at Solihull College.

"You mean the castle?"

He isn't the only one. Not a single visitor I meet that day has noticed the buildings and nobody knows they are architectural superstars. The medieval castle, right in the middle of the zoo, attracts far more attention.

"What's famous about them?" wonders Melissa, when I explain. "They're quite old-fashioned. I like that. That's very Black Country. It's quite industrial and the buildings suit it. I've been coming for years; I'd hate it if it changed."

It's only when you get into DZG that you realise how extraordinary it is.

The zoo runs in concentric circles around a hill, on top of which a motte-and-bailey castle was built in 1071, later owned by the earls of Dudley. The whole hill is covered with glorious beech trees, beneath which are not only limestone caverns – one said to be the size of St Paul's Cathedral – burrowed out for lime used as building material, fertiliser and flux in the steel furnaces, but also some of the most famous fossil beds in the geological firmament. There's even a trilobite called the "Dudley Bug" that used to be on the town's coat of arms.

It was the third earl who decided to fund the castle upkeep by building a zoo. Animal collections were fashionable among the rich at the time; he was given his by Frank Cooper, of marmalade fame. They were joined by Edward Marsh, a wealthy local businessman whose company claimed to make "the world's greatest sausage".

Lubetkin, a Georgian émigré responsible for buildings at Whipsnade and London Zoos – the Penguin Pool is still a favourite, despite having no penguins – was an obvious choice of architect.

At the moment, entry is not propitious; you park next to a disused cinema at the bottom of the hill and walk up to go in through the zoo shop. Out of the corner of your eye, you may notice the sort of entrance gate that would look at home in Miami: five peppermint-green concrete waves, interlocking over slender green columns of steel, framing the gigantic white letters Z – O – O.

"It was a place of wonderment," said Peter Suddock, the zoo's chief executive for 17 years. "You've got to remember that there was no television, hardly any photography in the papers, people were seeing live animals for the first time." When it opened in May 1937, more than 50,000 people poured under the green waves, bought rock and gobstoppers from two futuristic ovoid kiosks and swarmed on to the slender concrete terraces swooping above and around the animals.

There must be older people all over the West Midlands who remember their first weird, lanky giraffes, the polar bears plunging into the pool and the elephants picking up keepers in their trunks, to the joy of the crowds.

Zoos have changed profoundly in 70 years. You can't have polar bears any more, the last elephants went in 2003 and DZG now works on conservation, education and controlled breeding programmes with other European zoos. It is no longer fashionable to look down on animals, so many of the concrete terraces are now sealed off to the public, and only the sea lion pool is used for its original purpose. By modern standards the buildings are too small, too dark, not well enough heated for animals, though at the time they were radically innovative.

Today, the busy modern zoo works around its illustrious, dated infrastructure. Looking at the Bear Ravine, which, like most of the Tectons, was built into the caverns and sink holes made by the limestone workings, is like looking at a beautiful actress long past her prime; ravaged or not, the  bone structure is still fabulous.

Somehow the overgrown, unused terraces manage to convey a deck-and-railings effect, a sense of breezy confidence reminiscent of a Thirties cruise ship, though the view from the deck would have been an ocean of chimneys and a horizon of smoke; the West Midlands industrial landscape.

The structurally sound Tectons have been adapted: the Moat Café, once an open-sided, sinuous curve, is now a glassed-in Discovery Centre, and Itar the Asian lion – soon to be joined by two new females – prowls around the former Bird House, a drum-shaped building with a circular terrace. The interior, once lined with cages full of tropical birds, now contains sandpits full of Dudley toddlers. Itar lounges on the terrace like a bored billionaire, being photographed through the windscreen of a "Jeep" protruding ingeniously through a flanking wall.

All over the zoo, people are leaning on low parapets – some with their original ridged surfaces, like concrete corduroy – to look at the meerkats or marvel at the sea lions in their double-teardrop pool.

Half the pool once housed a killer whale; now the sea lions – a male and two females – flop portentously through the gap, all shivering, sleek, grey blubber, to torpedo through the salt water.

The funny thing is that even though we have television and many people have seen wildlife abroad the animals still delight. I find myself grinning idiotically at the sheer precision of sea lion frolics. Fiona Bond, from Wolverhampton, who has brought Emily, 11, and Charlotte, eight, along, is "not into zoos" and is startled to find how much her daughters are enjoying it. They have seen the lemurs and been in the Jeep. They love the gibbon hooting at the top of a beech tree.

A question that might fairly be asked by fans of the animals, rather than the buildings, is why all the fuss? Jon Wright patiently explains. "Lubetkin believed in Modernism's ability to improve society," he says. "You can view Dudley Zoo as a blueprint for a Modernist city, albeit one for animals, rather than humans."

Dr Jonathan Foyle, chief executive of WMF Britain, agrees: "It was about improving society, but also looking after animals – and the joy of seeing animals. It would be lovely to keep that spirit alive and do building conservation, too."

Peter Suddock is the first to admit that, on the long haul up from the Eighties, a nadir for many zoos, the priority was animal welfare and visitors. The buildings took a back seat. Now they are on the Watch List, he observes drily, "people are suddenly interested in Dudley".

With 235,000 visitors a year, almost 1,000 animals and a bit of surplus income, the zoo is planning a Heritage Lottery Fund bid. "We'll do a Tecton Trail, anyway, to explain why they're important," he says. "The animals are still the main thing, though; you wouldn't get these visitor numbers for the buildings without the zoo."

Dudley Zoo basics

Dudley Zoological Gardens & Castle (01384 215313; www.dudleyzoo.org.uk) are open from 10am to 3pm in winter, except for Christmas Day. Adult: £11.90 (including £1.10 Gift Aid), concessions: £8.70, child: £7.70, children under three free. Car parking £3 per day.

'Keeper for A Day' experiences cost £185 for one adult and £250 for two. 'Little Zoo Keepers' (8-13 years) cost £105 for one, £170 for two.

The legacy of Berthold Lubetkin

The Twentieth Century Society (020 7250 3857; www.c20society.org.uk) is 30 years old this year and organises tours and lectures on post-1914 British architecture. Contact the society for details for 2010 Tecton Tours at Dudley Zoo.

The World Monuments Fund Britain (020 7730 5344; www.wmf.org.uk) is a non-governmental organisation for the protection of cultural heritage in Britain and has just published its worldwide Watch List 2010.

Most surviving examples of Lubetkin's British work are in the capital. London Zoo's Gorilla House has gone but the Penguin Pool (1933-34), with its famous interlocking waddleways, is still there.

Grade I-listed Finsbury Health Centre (1935-38), Clerkenwell, can be seen from the outside; its future is currently under discussion.

Highpoint One (1933-35) and Two (1936-38), North Hill, Hampstead, are early apartment blocks that were originally planned as housing for workers but were soon sought after by middle-class fans (Lubetkin had a penthouse in the latter). They can be seen from the outside.