The UFO Bus Terminal of HungaryS

In 1552, a 200,000-strong Ottoman army was repelled by 2,100 Hungarian defenders at the Siege of Eger. The Ottomans left—but not before leaving behind a concrete stargate, converted in modern times to the town's bus terminal.

It doesn’t look half bad from street level either:

The UFO Bus Terminal of Hungary

Photo Credit: Fortepan, Hungarian Contemporary Architecture Centre