Bishop's Palace Bristol, Bath & Somerset

Built for the bishop in the 13th century, this moat-ringed palace is purportedly the oldest inhabited building in England. Inside, the palace's state rooms and ruined great hall are worth a look, but it's the shady gardens that are the real draw. The natural springs after which Wells is named bubble up in the palace's grounds. Famously, the palace's population of mute swans have been trained to ring a bell when they want to be fed.Guided tours are included in the admission price and run at 11am and 2pm (the palace), and 3pm (the grounds).