If you want to do the parliaments in order, start with the Rudolfinum on Namesti Jana Palacha It was originally built as a concert hall, but in 1919 it was converted into the Parliament building for the Republic of Czechoslovakia. The Nazi occupation resulted in the closure of the parliament, and its return to use as a concert venue.
After the war, the reformed National Assembly took up residence in the former stock exchange at the top of Wenceslaus Square. During the Prague Spring reform period in 1968, it was decided that Czechoslovakia would be federalised, and so a new extension, the Federal Assembly, was built on stilts over the former stock exchange. You got to hand it to them; the communists had the symbolism nailed.
After the collapse of communism, the old Federal Assembly building become a Radio Free Europe broadcast centre and the new post-communist parliament relocated back to the other side of the river, to the Lesser Thun Palace on Malastrankse Namesti. This building was the original home of the Landtag, the local Bohemian assembly during the period of Austro-Hungarian rule. Effectively therefore, the house has returned to its original 19th century location, with a few political upheavals along the way.