Troy was a city located in the far west of ancient Anatolia, part of Asia Minor, later Turkey. It was the site of the Trojan War, fought between the Greeks and Trojans circa 1200 BC. The Trojan king during the war was Priam.
The First Doctor, Steven Taylor and Vicki Pallister visited Troy at the end of the war and were partly responsible for the events leading up to the Greek victory. Here they met Katarina, who left in the TARDIS with the Doctor and an injured Steven, while Vicki stayed behind with King Priam's young son Troilus, with whom she had fallen in love. (TV: The Myth Makers)