The National Slate Museum is housed in the former workshops of Dinorwic slate quarry, near Llanberis. The quarry closed in 1969, and the Museum opened in 1972. It reopened in 1999 after complete renovation funded by the National Lottery. It is now part of the National Museum of Wales.
The museum is home to the largest working waterwheel in mainland Britain. Constructed in 1870 and 15.4m in diameter, it continues to power belt-driven machinery throughout the workshops.