I am curious how they excavated the rock to build Temppeliaukio church, particularly did they blast it with explosives? I'm curious since the location is in the heart of the city.
The Temppeliaukio church was completed in 1969 and it is one of Helsinki's main turist attractions.The architecs Timo and Tuomo Suomalainen won the preceeding achitectural competition in 1961, and their idea was to to cover a free-form rock excavation with a mathematical dome.
For exact information on the excavation please contact the secretary of the Finnish Tunnelling Association, Jouko Ritola. You may also find the links on the Tunnelling Association's homepace useful, see http://www.mtry.org.
There is a book by Maila Mehtälä called "Temppeliaukio", with what seems to be exact data on the excavating work. According to this source 12.400 solid cubic metres of bedrock was excavated. 4.100 kg dynamite, 3.500 detonating cord and 6.550 pieces blasting fuse were used. The excavation of the centre of the church required no extraordinary measures, but on an area of some 2 meters around the middle intensified presplitting was required. The immediate areas by the entrance and behind the pulpit had to be bolted.
An interview with one of the achitects can be found in "The fourth wave of rock engineering", a book published by the Tunnelling Association menitioned above. According to the architect the surface bedrock didn't pose any problems in the excavation process and there were only a few minor instances where the rock caused concerns. The rock gave way on the altar wall along an ancient crack, but this was used to create a sophisticated altarpiece.