At one point in time, all of the residents of Corfu lived inside the walls of the Palaio Frourio, or Old Fortress. Built in the 16th century by Venetians, Palaio Frourio lies at the eastern end of Corfu Town, separated by a moat. Some sections of the fortress offer breathtaking views of Corfu and its surroundings. Another major highlight of the fortress is the Church of St. George which was built by Venetians and utlitized by the British during their occupation of the island in the 1800s. 

Recent travelers say a visit to the Old Fortress is a must-do for first time visitors, but there isn't much signage to guide visitors around. 

You can enter the Old Fortress from 8 a.m. until 8 p.m. Admission costs 6 euros (about $7.50) for adults; children can enter for free.