Ruthin Gaol

This sombre building is the only Pentonville-style Victorian prison in Britain that's open to visitors. A free audio guide allows you to follow the sentence of an imaginary prisoner, while information panels in the cells fill you in on all the fascinating and grisly details of day-to-day prison life and the daring escapes of John Jones, the 'Welsh Houdini', banged up here in the 1870s. Pentonville-style prisons employed the 'separate system' of isolating and observing inmates.