Clérigos, Cerro del Grillo, Cerro del Padre and Cerro de la Bufa. These hills are starkly barren of vegetation, due to the semi-desert climate. The city is known for its clear air and clean streets, with garbage cans placed every ten meters in the city center. This city, along with Guanajuato and Taxco are along a route called the "Ruta de la Plata" or Silver Route. These cities are distinguished not only for silver but for the conservation of their colonial façades and narrow streets. Zacatecas conserves many of its original structures from the colonial period such as churches, colonial government buildings and monasteries and mansions built by rich miners in pink stone. Most of these buildings were constructed in the 18th century, when the silver flowing out of the mines was at its highest. These buildings have made the historic center of the city a World Heritage Site. Historic sites and attractions The Cerro de la Bufa, with its El Edén mine, is one of the most important symbols of the city and was the scene of the Battle of Zacatecas (called the Toma de Zacatecas in Spanish) in which Francisco Villa emerged victorious in 1914. At the top of this mountain is a museum and statues honoring Pánfilo Natera, Francisco Villa and Felipe Ángeles, which are related to this event. The site also contains an observatory, the Mausoleo de los Hombres Ilustres and the Chapel of Virgen del Patrocinio. The El Edén mine began operations in 1586 and principally produced gold and silver. According to legend the devil is supposed to be found in this parts due to the sound made when the wind whistles around the rocks. While operations began in the 16th century, its peak was reached in the 17th and 18th centuries. Despite the fact that there is still a significant amount of minerals left to extract, mining operations ceased in 1960, because the entrance is located in the middle of the city making this too hazardous. In 1975, the mine was converted into a tourist attraction. Today, visitors can take a small train which leads into the mountain for about a half a kilometer, then walk with a guide along some of the narrow passages. One of the things to see is an altar to the Santo Niño de Atocha. At night, the former rock crushing room of the mine has been converted into