Completed in 1969, Temppeliaukio Church is carved right from the bedrock in the center of Helsinki. The underground house of worship, called Temppeliaukion kirkko in Finnish, was designed by architect brothers Timo and Tuomo Suomalainen in the charmingly named Töölö neighborhood. On all sides of the circular church are roughly hewn stone, where sometimes water still seeps in to create miniature waterfalls. A dome coated with copper covers the rock church, with a skylight open in a belt below it to make the dome appear to hover. Even further below the church is a Cold War-era air raid shelter, which now serves as parking. Despite its cave-like appearance, Temppeliaukio Church actually has marvelous acoustics, where the sound beautifully bounces from the craggy stone. https://www.atlasobscura.com/places/temppeliaukio-church

The Cathedral, by Carl Ludvig Engel, rising on the northern side of the Senate Square is the stage of national and academic festive services and one of the most popular tourist sights. http://www.visithelsinki.fi/en/see-and-experience/sights-and-attractions/helsinki-cathedral