The pit was first worked in 1860, called "Big Pit" because it was the first shaft in Wales large enough to allow two tramways. In the late 1870s the shaft was deepened to 293 feet. By 1908, Big Pit provided employment for 1,122 people, but this number gradually decreased until by 1970 the workforce only numbered 494. It closed on February 2 1980.
The mine reopened for visitors in 1983. As with all national museums in Wales, admittance is free. The site was redeveloped in 2003, with design work from TACP/Brooke Millar Partnership, Powell Dobson Partnership and Haley Sharpe, with Davis Langdon providing cost and project management services.
In 2005, it won the prestigious Gulbenkian Prize.
Big Pit is not a sanitised Disney attraction or a theme park, the pit props and steel bands are not for show but to hold up the roof, the water flowing down the tunnel towards the cages is real apart from the fact it now flows down a channel rather than over the miners feet.
The pit is covered by mining regulations, similar to that of a working pit. Visitors wear a plastic hard hat and ‘safety lamp’, another piece of kit is the re-breather emergency supply, breathing this in an emergency will filter foul air for approximately one hour giving a chance for survival and escape.
Contraband must be surrendered such as anything containing a dry cell battery from watches to mobile phones. The dangers of the mine are real, the safety posters on the stages of Carbon Monoxide poisoning serve as museum pieces and as real reminders of the dangers of underground. Automatic gas monitoring systems are discreetly positioned around the tunnels as are emergency telephone systems.