Construction started in 1926 and was completed in 1929, at a cost of 17 million U.S. dollars, using 5000 workers. It was the tallest building in Havana until the 1950s.
It houses the world's third largest indoor statue; the Statue of the Republic, Hostess of the National Capitol of Cuba.
Many people think it is a copy of the U.S. Capitol, however it is not a replica. According to wikipedia, "It is similar to that in Washington D.C, but a meter higher, a meter wider, and a meter longer, as well as much richer in detail."
The actual construction time was 3 years, 3 months and 20 days.