Troy, or Ilium, was an ancient city in Eurasia on Earth.
According to the Greek author Homer, the city was besieged and destroyed by the Greeks in a war in about 1200 BC. Upon seeing Yeoman Teresa Ross, Trelane remarked on her beauty inquiring if hers was "the face that launched a thousand ships and burnt the topless towers of Ilium?" (TOS: "The Squire of Gothos")
The city was rediscovered in the 1870s by the German archaeologist Heinrich Schliemann. According to Galen, this discovery counts among the greatest archaeological discoveries of all time. (TNG: "The Chase")
Henry Janeway compared himself to Hector slipping past the Greek lines and bringing supplies to the "embattled city of Troy", when he brought supplies to his store Alexandria Books in late 2000. (VOY: "11:59")