Troy was an ancient city on the coast of Turkey. When Paris, a Trojan prince, abducted Helen, the wife of Menelaus of Greece, the city was besieged by the Greek armies. The siege went on for ten years and is described in Homer's 'Iliad'.
Troy was eventually defeated when the Greeks played a trick. They pretended to abandon the siege, but left behind a large wooden horse, which the Trojans took to be a gift. Despite Cassandra's warnings, they towed the horse into the city. Greeks poured out of it and sacked Troy. A few Trojans, including Aeneas, survived.