Temppeliaukio Rock Church, Töölö, Helsinki, Finland

Temppeliaukio Church (Finnish: Temppeliaukion kirkko, Swedish: Tempelplatsens kyrka) is a Lutheran church in the Töölö neighborhood of Helsinki. The church was designed by architects and brothers Timo and Tuomo Suomalainen and opened in 1969.
The Temppeliaukio/Tempelplatsen (Temple square) was selected as a location for a church in the 1930s, but the plan by J. S. Siren, the winner of the second competition to design the architecture of the church, was interrupted in its early stages when World War II began in 1939. After the war, there was another architectural competition, which was won by Timo Suomalainen and Tuomo Suomalainen in 1961. For economic reasons, the suggested plan was scaled back and the interior space of the church reduced by about one-quarter from the original plan. Construction finally began in February 1968, and the rock-temple was completed for consecration in September 1969.
The interior was excavated and built into the rock but is bathed in natural light entering through the glazed dome. The church is used frequently as a concert venue due to its excellent acoustics. The acoustic quality is ensured by the rough, virtually unworked rock surfaces. Leaving the interior surfaces of the church exposed was not something that was in the original plans for the church. Conductor Paavo Berglund told the brothers of his experiences in the best music halls, and the acoustical engineer Mauri Parjo set out requirements for the wall surfaces. The architect brothers discovered that they could fulfill all the requirements by realising their own idea of leaving the rock walls exposed in the Church Hall. This idea the brothers already had when planning the competition entry, but they had been afraid to present it thinking it too radical for the competition jury.
The Temppeliaukio church is one of the most popular tourist attractions in the city; half a million people visit it annually. The stone-hewn church is located in the heart of Helsinki. Maintaining the original character of the square is the fundamental concept behind the building. The idiosyncratic choice of form has made it a favorite with professionals and aficionados of architecture.