The Pantheon is one of the greatest ancient buildings ever built. It was first built as a Roman temple during the reign of Augustus in 128 AD (thats over 118 years ago). The temple itself still stands today:
The roof of the Pantheon was the largest dome Rome ever constructed - it even has a hole on top called the oculus that is open to the sky. Yes this means that during a rainstorm, water would enter the temple. Luckily, drainage would drain the water out and keep the temple from flooding.
Fun fact : The dome of the temple was made out of concrete (yes romans had access to concrete!) and is still intact from ancient times!