Which country has a building on his flag?

The flag of Gibraltar has a three-towered castle from which hangs a key.

The flag of Cambodia has a building - it looks somewhat like a palace with three towers. It is red with a band of blue at the top and the bottom.

The building on the flag of Cambodia is Angkor Wat, a temple built during the early years of the 12th century by Suryavaram II, that honors the Hindu god Vishnu.