In 1502, at the request of the Turkish sultan, Leonardo da Vinci came up with the design for a stone bridge that would cross the Golden Horn, an inlet of the Bosporus located on the western side of Constantinople (modern-day Istanbul). With a span of some 240 meters, it would have been the longest bridge in the world—if it had been built. Now, more than 500 years after the sultan rejected da Vinci’s design, a team of students and volunteers in the Finnish town of Juuka are in the process of constructing a scale model of the original drawing—out of ice.
Over the past three years, the Built Environment department of the Eindhoven University of Technology (TU/e) in the Netherlands has spearheaded the construction of the world’s largest ice dome (30 meters across) and the world’s highest (30 meters high, based on the design of the Sagrada Familia cathedral in Barcelona). Last week, a TU/e-led team began construction of what will be the world’s longest ice bridge in Juuka, a town in the North Karelia province of eastern Finland. For the design, they are using an original drawing made more than 500 years ago by none other than Leonardo da Vinci, the painter, architect and inventor behind such masterworks as “Mona Lisa” and “The Last Supper.”
This isn’t the first time modern builders have constructed a homage to da Vinci’s ambitious, never-built 1502 design for what is now the Galata Bridge over the Bosporus in Turkey. In 2001, an organization called the Leonardo Bridge Project constructed a wooden bridge based on the design in Norway. The team in Juuka is building their scale model of da Vinci’s drawing out of a substance known as pykrete, a mixture of water and two percent paper fiber. The fiber makes water in its frozen state three times as strong as normal ice and 10 times as tough.
The Juuka ice bridge will be 16 feet (five meters) wide and 213 feet (65 m) long, with a free span of 115 feet (35 m). These measurements will make it the longest ice bridge ever constructed. To build the structure, a team of students and volunteers spray the water mixture in layers over an inflated balloon, which serves as a mold for the bridge. Once the bridge is strong enough, the balloon will be removed. According to a TU/e press release about the project, the bridge “has the same construction principle as that of Da Vinci’s: the only load on the whole structure is compression.” After the ice bridge melts in the spring, the paper fiber left over will be used as compost.
The bridge construction team will work in staggered shifts, with work continuing 24 hours a day, seven days a week, for seven weeks. The students cannot stop for any length of time, as the equipment would freeze; the high temperature in Juuka early last week was 12 degrees Fahrenheit. The university press release describes the working conditions as “severe.” In total, some 150 students and volunteers from the Netherlands as well as Belgium, England, Scotland, Portugal, Switzerland and Finland will take part in the project. The team expects to complete the bridge on February 13.
Though only pedestrians will use the Juuka ice bridge, the construction designers have calculated that the structure will be strong enough to easily bear the weight of a two-ton car. During the opening ceremony, held as part of a larger ice festival in Juuka, they plan to show off the bridge’s strength by driving a car over it.