Not a cave but a room blasted out of the living granite under a Helsinki city block, roofed with a copper spiral and lit by 180 skylights cut in the rock. The Finnish bedrock is so solid that Helsinki uses it constantly: there are swimming pools, car parks, a whole shelter system and even a data centre carved underground. This is the most beautiful example, and the acoustics are extraordinary. PUBLIC (a working church; check service times), Helsinki, Finland.
Finland
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