Following the Estonian Declaration of Independence in 1918, a building to house the parliament of the republic was erected at the site of the former convent building of the Teutonic Order. Taking two years to complete, it was finished in 1922, and designed by architects Eugen Habermann and Herbert Johanson. Although its exterior is traditionalist, the interior is Expressionist in style - supposedly the world's only Expressionist parliament building. During the subsequent periods of Soviet, German, and a second Soviet occupation (1940–1991) the Riigikogu was disbanded. The castle and the building of the Riigikogu were however used by the Supreme Soviet of the Estonian SSR during the second Soviet occupation.
Information from:
en.wikipedia.org/wiki/Toompea_Castle