Tower of London, United Kingdom
The fortress has served as a royal palace, an armory, a treasury and even a zoo, housing elephants, monkeys and rhinoceroses. Now, only ravens live in the tower, which is almost 1,000 years old. They are known as the guardians and legend has it that the kingdom and the tower will fall if they ever leave. To make sure that this does not happen, they all have one wing trimmed.