The Antikythera mechanism (pronounced /ˌæntɨkɨˈθɪərə/ ANT-i-ki-THEER-ə or pronounced /ˌæntɨˈkɪθərə/ ANT-i-KITH-ə-rə) is an ancient mechanical computer designed to calculate astronomical positions. It was recovered in 1900–01 from the Antikythera wreck. Its significance and complexity were not understood until decades later. Its time of construction is now estimated between 150 and 100 BCE. The degree of mechanical sophistication is comparable to a 19th century Swiss clock. Technological artifacts of similar complexity and workmanship did not reappear until the 14th century, when mechanical astronomical clockswere built in Europe. Jacques-Yves Cousteau visited the wreck for the last time in 1978, but found no additional remains of the Antikythera mechanism. Professor Michael Edmunds of Cardiff University who led the most recent study of the mechanism said: "This device is just extraordinary, the only thing of its kind. The design is beautiful, the astronomy is exactly right. The way the mechanics are designed just makes your jaw drop. Whoever has done this has done it extremely carefully ... in terms of historic and scarcity value, I have to regard this mechanism as being more valuable than the Mona Lisa." The device is displayed at the National Archaeological Museum of Athens, accompanied by a reconstruction made and donated to the museum by Derek de Solla Price. Other reconstructions are on display at the American Computer Museum in Bozeman, Montana, the Computer History Museum in Mountain View, California, the Children's Museum of Manhattan in New York, and in Kassel, Germany.