The most famous of the silver mines that made Guanajuato one of the richest cities in the Spanish empire, on the ridge above the centre at the village of La Valenciana. The Bocamina San Cayetano is the upper entrance to the working shaft; guides take small groups down a steep wooden staircase to the first level for a short underground walk through cool, damp galleries. The mine still produces silver intermittently.
Combine with a visit to the adjacent church of San Cayetano. About fifteen minutes by taxi from the centre.