Embedded in the floor in the centre of the main hall of the Capitolio in Havana Centro is a replica 25 carat diamond, which marks Kilometre Zero for Cuba. Highway distances between Havana and all sites in Cuba are calculated from this point. The original diamond, said to have belonged to Tsar Nicholas II of Russia and have been sold to the Cuban state by a Turkish merchant, was stolen on 25 March 1946 and mysteriously returned to the President, Ramón Grau San Martin, on 2 June 1946. It was replaced in El Capitolio by a replica in 1973.