The cathedral represents the Russian-byzantine style churches that were popular in Russia during the 14th century. It was built using red bricks, most of which actually came from the Fortress of Bomarsund which was demolished as a result of the demilitarization of the Åland Archipelagoafter the Crimean War. Approximately 70 000 bricks were recycled from the fortress. Only the outer walls of the cathedral were brand new bricks.  

On the roof there are 13 gilded flame-shaped domes, which represent Jesus and the 12 apostles. The domes have been gilded 4 times throughout history, latest being 2004-2007. 

The church is approximately 33 meters tall from the ground to the highest cupola which symbolizes the age of Jesus Christ when he died for our sins.

The cathedral is supported by 4 humongous Doric columns made out of polished granite. Each one was chiseled from a single block of granite which were brought from the coast of Helsinki. All of the building materials for the cathedral were transported to the cathedral with a branch line (small railway) which was constructed specifically for the purpose of building the cathedral. The iconostasis covers the whole east wall and the holiest place in the cathedral, the altar, is situated behind it.