Unioninkatu

thumb|right|Unioninkatu viewed to the north from the Senate Square. On the left are the main building of the University of Helsinki and the [[Finnish National Library, on the right are the towers of the Helsinki Cathedral and the Holy Trinity Church. The tower of the Kallio Church is located at the northern end.]] thumb|right|Unioninkatu viewed to the south towards Kaartinkaupunki: the intersection of Unioninkatu and [[Aleksanterinkatu to the southwest of the Senate Square.]] thumb|right|Unioninkatu viewed to the south at Metsätalo. thumb|right|The northern end of Unioninkatu viewed towards the Kallio Church from the Kaisaniemi roundabout. On the left are the Kaisaniemi Park and the Kaisaniemi botanical gardens. thumb|right|Eugen Hoffers, view from Ulrikanporinvuori (now known as Tähtitorninvuori) to the north, on the left is Unioninkatu, in the middle is the German Church in Helsinki, 1867. Picture from the City Museum of Helsinki. Unioninkatu (Swedish: Unionsgatan, both meaning "Union Street") is one of the key streets in the historic centre of Helsinki, Finland. It stretches from the Tähtitorninvuori hill to the Pitkäsilta bridge and is about 1.5 km long. Its southern part is located in Kaartinkaupunki up to the Esplanadi park, while the northern part acts as the border between Kruununhaka to the east and Kluuvi to the west. The street functions as a local assembly street.

In the south, Unioninkatu is directly continued by the short street Kopernikuksentie leading to the gate of the Helsinki University Observatory. In the north, Unioninkatu is directly continued after the Pitkäsilta bridge by the street Siltasaarenkatu leading to the Kallio Church. Together these three streets form a 2.5 km long street line called Unioninakseli, the longest continuous straight street line in central Helsinki.