This "Church of the Rock" is about 2 blocks west of the National Museum in the Töölö residential district west of Mannerheimintie. Only the domed copper roof and a circular curtain wall of granite blocks are visible from outside. It was designed by two architect brothers, Tuomo and Timo Suomalainen, who were inspired by the shape of Helsinki's archipelago. They chose a rocky outcrop rising some 12m (40 ft.) above street level. The interior walls were blasted from bedrock, and the church's low-rise format and ecosensitive design appealed to residents of neighboring apartment buildings. Its interior is flooded with light from a circular skylight that rings the lower edges of the low slope of the dome. Because of its superb acoustics, the church is often used as a concert hall.