The Hassan II Mosque

The third largest mosque in the world, the top two are in Saudi Arabia
apparently. Holds 25,000 people with room outside for a further
80,000. Build 1986-1993. At night a laser shines from the top of
the minaret towards Mecca.

Very impressive use of space, something I found lacking in Spanish
cathedrals - they have a big building and then fill it with junks so
you don't get the 'wow!' factor from the space.
...