Big Pit National Coal Museum
Old Rectory Big Pit
About 25 minutes by car.
www.museumwales.ac.uk/bigpit Telephone 02920 573650
Five stars on TripAdvisor.
Open 9.30 am to 5.00pm daily with Underground Tours (best bit) between 10.00 am and 3.30 pm.
Free entry. Children must be over 1 metre tall for the underground tour.