Guanajuato, located in the central region of Mexico, is the capital of the state with the same name. Its narrow valleys make the city's streets winding and narrow, with many alleys that cars cannot pass through. Some are long sets of stairs up the mountainsides. The historic center contains colonial-era mansions, churches, and other structures, most of which are made of pink or green sandstone. This area and its mines were declared a World Heritage Site by UNESCO in 1988. This city developed due to the abundance of minerals in the mountains nearby and La Valenciana, one of the mines, accounted for two-thirds of the world's silver production.