Worth a visit & its all free
To discover the depths descend 140 metres underground down one of Britain's oldest working mines. Your guide will take you around the workings, sharing his mining experiences with you. The tour lasts approximately 1 hour and 15 minutes. Each visitor is provided with a hat, belt and battery, so that the true atmosphere of working life underground is captured.
The last underground tour daily is at 3.15pm; simply book in at Reception on arrival."
On the surface theres the original pithead, complete with steam winder, the baths, medical centre & plenty of mining machinery & artefacts. Also Hope Pit nearby on the site with hands on interactive models, etc
More info at NCM - The National Coal Mining Museum for England