The Suomenlinna Church in Helsinki, Finland, was built in 1854 as an Eastern Orthodox garrison church for the Russian troops stationed at the Suomenlinna sea fortress. The fortress comprises five islands joined together by bridges, and the church is the central feature on the island of Iso Mustasaari, located at its highest point. It is surrounded by other fortress buildings, but the old parade ground is immediately to the east, and a park lies immediately to the south. It is oriented southwest to northeast so that it would align with the Crownwork Ehrensvärd defense front located to the southwest of the church.
Before the design and construction of the Orthodox church, plans were drawn up in the 1820s by architect Carl Ludvig Engel for a church on the same site, but designed in the neoclassical style in keeping with the rest of buildings at the fortress and the buildings in the capital city, Helsinki.
Wikipedia https://en.wikipedia.org/wiki/Suomenlinna_Church
Official Website http://www.helsinginkirkot.fi/fi/kirkot/suomenlinnan-kirkko
Coordinates 60°8'52.225" N 24°59'10.936" E