Heritage Open Day: See inside this watch-tower on York's City Walls. Rarely open to the public, our volunteers are on hand to show off the spiral staircase, Tudor toilet and timber roof. Find out about the history of the Walls and look out for any approaching invaders! The Tower was built around 1505 where the City Walls ended on the banks of a swollen river Foss, with York Castle on the opposite bank. The narrow, 500 year old stairs twist to the right as you go up, making it difficult for a right-handed attacker to use a sword (or any weapon) as effectively as a defender facing him from above. The stairs take you up to the first floor room, which has a small twisted corridor off it leading to the garderobe, for human waste to drop straight into the river.