How do you solve a problem like a penguin pool?

The white slides of London Zoo’s penguin pool curve down into the shallow blue waters. The spiral seems to glide through the air, a feat its flightless inhabitants can only dream of. When it opened, the penguin pool — designed by the avant-garde modernist architectural practice Tecton, led by the Russian émigré Berthold Lubetkin — was promptly lauded as the "most picturesque corner of London Zoo”. Crowds flocked to see the creatures; Princesses Margaret and Elizabeth visited regularly; and the Daily News announced that “the lovely lines of the penguin pool at the London Zoo are famous all over the world”.

Yet today, the pool is empty, and has been for the better part of the past two decades, bar some porcupines who sidled around for a few years. The last penguin waddled out of the enclosure in 2004 and the pool has been empty of critters since 2009. But even now, almost a century later, it dazzles. The pool is celebrated in architectural circles, including by Historic England, which listed the building in 1970, and by modernist nerds such as the brutalist-loving 20th Century Society (known as C20 Society).

The debate over what should be done with the abandoned pool has gone on for over a decade. The C20 Society’s Oli Marshall says it should be used as a stage for cultural events. Others, like Sir Peter Wynne Rees, professor of planning and urban places at UCL, would prefer it to be adapted to become a suitable enclosure for penguins. And Lubetkin’s own daughter would like to see it "blown to smithereens". So just what went wrong with the building once dubbed “the mascot for the modernist movement in Britain" — and what is its future?