The chief town on the island of Lesbos, Mytilíni (or Kástro; pop. 24,000), lies in a bay on the east coast, on the site of ancient Mytilene. A breakwater, which is also a popular promenade, protects the harbor, on which the commercial activity of the town is centered. Above the tiled roofs of the low houses, some of them fronted by colonnades,
rises the characteristic dome of the church of Áyios Therapón (late 19th C.), the architecture of which betrays western influence. Between the present south harbor and the ancient harbor to the north is an area of low ground, once traversed by a canal, which separates the main part of the town from the massive Gattelusi castle.