The Golden Horn Bridge designed by Leonardo da Vinci in 1502 is finally being built, although while the great Renaissance man originally intended the structure to traverse the Bosphorus in Istanbul, its belated construction is in fact taking place in Juuka, Finland. Furthermore, instead of creating the bridge out of stone, as per the original design, the engineers behind the project are using ice.

Spanning 35 meters (115 feet) across a quarry, the so-called Bridge in Ice will be the longest ice bridge ever constructed and is expected to be completed by February 13. This, however, will depend on the weather, with the threat of unseasonable warmth raising the prospect of the bridge not freezing quickly enough to meet this deadline.

Fortunately, the conditions have so far been ideal for the construction of the bridge, with temperatures in Juuka hovering around the -30°C (-22°F) mark since work began on December 28, 2015. To create the structure, around 150 students led by a team from the Eindhoven University of Technology are working in shifts around the clock, ensuring equipment is never left idle so that it doesn’t freeze.

^{Shown is da Vinci's original sketch for the Golden Horn Bridge. Public Domain}

The bridge is being created using ice infused with paper fibers, which make it up to three times stronger and 20 times more ductile than normal ice. To construct it, the team are spraying thin layers of this mixture of water and paper onto the surface of a giant inflatable round mould, at which point it freezes almost instantly. Each layer is only a few milimeters thick, and once enough of them have been built up to provide sufficient stability for the ice to stand on its own, the mould – which has been compared to an enormous balloon – is removed.

Once finished, the bridge will be open to pedestrians only, although the team are confident that it could also support the weight of a vehicle. To prove this, they will drive a car over the bridge during the opening ceremony. Later in the year, when the ice melts, the paper fibers will be used for compost.