1 April, 2025

Martha Henriques Hello. Most modern buildings' foundations are made out of reinforced concrete and steel – but, despite their strength, few foundations today could last as long as Venice's. For over 1,600 years, this watery city has been kept afloat by millions of short wooden piles – discover the full story below. Also in this edition: how researchers are removing "forever chemicals" from water.

THE BIG PICTURE How do you re-home rhinos? Upside down Researchers are transporting rhinos upside down with the help of war-worn helicopters. Credit: Micky Wiswedel/WWF This incredible photo shows a 1,300kg (2,865lb) rhinoceros dangling by its feet from a helicopter flying over South Africa. Helicopters have revolutionised rhino conservation in southern Africa over the past decade, helping move these endangered horned herbivores to safer areas, away from poachers. Some of these helicopters were used during the Vietnam War and are still riddled with bullet holes. Read more in Riley Farrell's story.

CLIMATE CONVERSATION  The ancient forest that supports Venice Venice is kept afloat by an inverted forest. Credit: Emmanuel Lafont Anna Bressanin, New York City Venice is one of the few cities in the world to have a birthday. As the legend goes, on 25 March 421AD a carpenter from nearby Padova set down the first two stones of the San Giacomo of Rialto church. In fact, the city was built gradually during the final decades of the Roman Empire, as people from further inland sought refuge on the small islands of the lagoon, where the Visigoths and the Huns wouldn't venture. How did the Venetians manage to build a marvellous city of stone on a wobbly base of mud and water?  Locals would answer that Venice, which is shaped a little like a fish when viewed from the air, is kept afloat by an upside-down forest. As a Venetian, I never found this strange, nor questioned the science and engineering behind it. But when I casually mentioned it to my colleagues, they seemed intrigued. Today, most buildings' foundations are made of concrete and steel, and have a standard guarantee to last 50 years. Meanwhile, Venice's archaic system of short wooden piles, stuck by hand in the mud, has held up a city for 1,604 years. The piles don't even reach the bedrock, they keep the buildings up thanks to friction, and there are millions of them: there are 12,000 tree poles under the Rialto bridge alone, and 10,000 oak trees under the San Marco Basilica, built in 832AD.

Venice's wooden piles don't even reach the bedrock, they keep the buildings up thanks to friction. Credit: Emmanuel Lafont Forest conservation was a positive side effect. A city relying on wood both for its buildings and its ships couldn't afford to deplete this resource. Nicola Macchioni, research director at the institute for bioeconomy at Italy's National Council for Research, told me that the first ever sylviculture document in Italy (dating back to 1111AD) is from the Magnificent Community of the Fiemme Valley, a cooperative of wood owners to the north-west of Venice. This early conservationism didn't surprise me too much. At the old fish market in Venice, next to the Rialto Bridge, there is still an ancient sign stipulating the minimum size a fish must be to be sold legally. Eels can't be shorter than 25cm (10in), oysters can't be smaller than 5cm (2in), mussels can't be less than 3cm (1in) and so on. A 1173 edict established these rules, to allow fish to reproduce at least once before being eaten. Seminal writer Italo Calvino loved Venice's communion with natural elements such as water, land and air. All the 55 fantastical cities he describes in his 1972 novel The Invisible Cities are based on Venice, because he saw the lagoon town as an archetype of all metropolises. As the main character of his novel says: "Every time I describe a city, I am saying something about Venice." Read more about the ancient forest that supports Venice here.