A historical marker on the building provides text in Finnish, Swedish, and English. The English text reads:
"BOCK BUILDING
Aleksanterinkatu 20
Unknown designer, completed in 1763. Renovation 1816-1818, architect Carl Ludvig Engel. The Magistrate and merchant, Gustaf Bock, built the house as his personal residence. In 1801 it became the official residence of Major of Helsinki, a so-called 'ordonanssi-house'. From 1808, the property served as officers' quarters until it was converted to the palace of the Governor between 1816 and 1818. After 1837, the building became the Town Hall and then served as the City Hall from 1882 to 1913. The building still houses city offices."
The following additional information is from the Virtual Helsinki website:
"The oldest of the houses in the Lion Block is the one built in 1763 by the merchant and magistrate Gustav Johan Bock. In addition to the main wing on what is now called Aleksanterinkatu, it had a side wing running along the intersecting Katariinankatu.
One of the annexes built on the plot in the 19th century was a stone one opening onto Katariinankatu. The upper floor of Bock House was originally given over to the family apartments and salons, some of which were rented out. Distinguished visitors to the city were also received in the imposing house. Legend has it that Kings Gustavus III and Gustavus IV Adolf of Sweden enjoyed the hospitality of Bock House while visiting Helsinki. In 1801 the house became the property of the Swedish Crown.
Governor General's residence
Following the war of 1808-1809 Finland was separated from Sweden and united with Russia as an Autonomous Grand Duchy, remaining so until it became an independent republic in 1917.
His Imperial Majesty declared that his Grand Duchy must have a capital worthy of its new status, and as part of the vast plan for the new city centre, a complete facelift was ordered for Bock House. The former occupants had by that time moved out, and in 1808 the staff of the Russian garrison stationed in Helsinki took up residence there. In 1816-1818 a third floor designed by C.L. Engel was added to the house, along with an annex complete with a banquet hall and minstrels' gallery. The gable was smartened up with four Ionic columns and a balcony, and the interiors were painted in striking colours and adorned with murals and stucco ornaments. The wings opening on to Katariinankatu were likewise made to conform to the Neoclassical design.
In the late 18th century For nearly two decades Bock House served as the official residence for the Governor General, the Tsar's representative in Finland. Various distinguished guests were also accommodated there, including Tsar Alexander I, Grand Duke of Finland. It was from the Bock House balcony that he greeted the people of Helsinki gathering in Senate Square to pay their respects to him. Later the house was visited by Tsar Nicholas I.
The Governor Generals having moved into their new residence in what are now the Cabinet rooms on the South Esplanade in 1838, Bock House became Helsinki Town Hall. Its new occupants also included the Magistrates. The changing cityscape: A city tried by war and hunger, Helsinki was also plagued by fire. In the late 18th century houses began to be built of stone instead of wood, and the street scene gradually changed.
The Empire HallCourt, the auction rooms, and a prison. During the 19th century there was a police station in the Katariinankatu wing, along with facilities for male prisoners in the city gaol. The Town Council, chaired by Senator Leo Mechelin, convened for its first session in the assembly hall - nowadays known as the Empire Hall - in 1875.
The Empire Hall is one of the most beautiful halls in Helsinki. Restored in 1988, it is decorated in shades of light green. The original stucco ornaments on the ceiling have been restored and among the portraits on the walls is one by Albert Edelfelt of Senator Leo Mechelin. The Magistrates' Court and City Administrative Court occupied Bock House from 1913 to 1985. During the renovations carried out in 1985-1988, the layout and colouring of the interiors were restored in the spirit of Engel's plans.
The City of Helsinki nowadays uses Bock House and the Empire Hall for official receptions and gala occasions. The house also has meeting and reception rooms for the parties represented on the City Council and is the home of the City Information Office."
Additional information is available in the Finnish Wikipedia at (visit link).