Newcastle was funnily enough named after a castle, however there is nothing new about it any more. I think the city itself is something in the region of 900 years old, and therefore presumably so is the castle! It is built on the sight of an old roman fort, and was essentially the place from which the city grew and radiated out from. The castle was an important stronghold in the defences against the Scots, which was a regular requirement in medieval times.
The castle is up the hill from the Quayside in what must have been a fairly dominating position in its day, but what now is surrounded by many other buildings. It is adjacent to Newcastle Cathedral, which is distinctive with its lantern shaped spire.
The castle is obviously a bit of a ruin these days, but some of the walls are still standing, and the Keep is still there. There are also remains of the old city walls which can be seen near Stowell Street, which is nowadays Newcastle’s chinatown!