This concept by architecture firm NBJJ envisions fold-away natural rinks that could turn London's River Thames itself into a temporary place to skate. The concept, called Frost Flowers, uses foldaway structures that could be neatly trussed up during the summer and unfurled come winter. As the petals unfold, they'd dip just below the river's surface to collect water. Then, they'd be lifted slightly, frozen, and left to create a neat, circular ice rink.
In the 18th and 19th century, the Thames often froze during the winter, sometimes for months at a time. Impromptu Frost Fairs would then take place, where locals skated on the frozen surface. But new bridges allowed the river to flow more easily, which made it harder for the river to freeze over, and the last Fair occurred in 1814.
The Frost Flowers would be, according to NBJJ, an attempt rekindle a little of that magic, "bringing public ice-skating, markets and exhibitions to the people of London". The firm reckons that the structures could be "installed and adapted to multiple locations throughout London and potentially many other city rivers around the world".