From the video's description:
The Antikythera Mechanism: ... is the oldest known scientific computer, built in Greece at around 100 BCE. Lost for 2000 years, it was recovered from a shipwreck in 1901. But not until a century later was its purpose understood: an astronomical clock that determines the positions of celestial bodies with extraordinary precision. In 2010, we built a fully-functional replica out of Lego. ...
More on the Antikythera Mechanism:
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, but its complexity and significance were not understood until decades later. It is now thought to have been built about 150–100 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 clocks appeared in Europe.
Jacques-Yves Cousteau visited the wreck for the last time in 1978, but found no more 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 in the Bronze Collection of 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 Children's Museum of Manhattan in New York, and in Kassel, Germany.