Dartmoor Prison is one of England's most famous — and most forbidding — places of incarceration. Still in operation as a Category C men's prison, it dominates the skyline of Princetown with its granite walls and watchtowers, a bleak silhouette entirely in keeping with the surrounding moorland. The prison is not open to visitors, but it can be clearly seen from the road.
The adjacent Dartmoor Prison Museum (in the former gatehouse building) tells the story of the prison from its Napoleonic origins through the 20th century. It holds original artefacts, prisoner records, and a reconstructed cell. The museum is small but genuinely absorbing and gives a good sense of what life inside was actually like. Opening hours are limited — check before visiting.