The Bohemian State Diet (Landtag) used to meet in Sněmovní street. Many elected members of this assembly went on to play an important role in the political events of 1918. The Revolutionary National Assembly, formed immediately after the announcement of Czechoslovak statehood met for the first time in the Thun Palace on 13 November 1918, codifying the new State and proclaiming Tomáš Garrigue Masaryk president the day after. It also affirmed the members of the first Czechoslovak Government.
Source: https://www.prague.eu/en/object/places/3154/the-thun-palace-thunovsky-palac