Colossal Kallio Municipal Office Building [Kallion Virastotalo] is located by the Eläintarhanlahti bay in Hakaniemi, Kallio district of Helsinki. It forms a pair with the neighbouring Circle House. The two monumental office buildings represent a strong modernist approach to architecture. Both buildings, designed by architect couple Kaija and Heikki Siren, were developed in the 1960s. Kallio Municipal Office Building was completed in 1965 and the commercial office building Circle House in 1968.

Kallio Municipal Office Building consists of a towering 11-storey high main building with lower wings surrounding the main building mass. Window bands and light ceramic facing tiles are characteristic features of the façade architecture, along with the monumental scale of the building.

The plot of the office building has a large rock which is visible on the side of Toinen Linja street of the building. The rock is a metaphorical detail of the site, the district Kallio which is also in the name of the building, means rock in Finnish.