Dominating tiny Helgeandsholmen are the buildings of Sweden's parliament, Riksdagshuset (riksdagen.se). The older section, dating from 1905, includes the two chambers used when the country had a bicameral parliament; in 1971 Sweden changed to a unicameral system, so a modern chamber was constructed in the 1980s inside what used to be the Bank of Sweden.
All this and more is explained on the fascinating, hour-long tour (in English at 1.30pm on Saturday and Sunday) which offers a compelling glimpse into the Swedish system of consensus-building government. Places are limited to 28 people so line up early.