When visiting the campo de fiori in Rome you will see in the middle of the market place a statue of Giordano Bruno. He lived from 1548 - 1600 and he's known for his cosmological theories. He believed that the stars were distant suns surrounded by their own (exo)planets and he even mentioned the possibility that these planets could even foster life. He also insisted that the universe is in fact infinite and could have no celestial body at its center.
He was put in prison and after his 7years trial he was convicted by pope clement VIII and burned at the stake.
