The oldest part of Sheffield, at the meeting of the rivers Don and Sheaf where Sheffield Castle stood until it was demolished after the Civil War. Mary, Queen of Scots was held there for much of her fourteen years of custody under the Earl of Shrewsbury. Castle Market covered the site from the 1960s until it was demolished in 2015, and the area is now being opened up as a park, with the River Sheaf brought back into daylight and the castle remains displayed.
Wikipedia: Castlegate