Tlalpan is one of the 16 administrative boroughs of the Federal District of Mexico City. It is the largest borough, with over eighty percent under conservation as forest and other ecologically sensitive area. The rest, almost all of it on the northern edge, has been urban since the mid-20th century. When it was created in 1928, it was named after the most important settlement of the area, Tlalpan, which is referred to as “Tlalpan center” to distinguish it from the borough. This center, despite being in the urbanized zone, still retains much of its provincial atmosphere with colonial era mansions and cobblestone streets. Much of the borough’s importance stems from its forested conservation areas, as it functions to provide oxygen to the Valley of Mexico and serves for aquifer recharge. Seventy percent of Mexico City’s water comes from wells in this borough. However, the area is under pressure as its mountainous isolated location has attracted illegal loggers, drug traffickers, and kidnappers—but the most serious problem is illegal building of homes and communities on conservation land, mostly by very poor people. As of 2010, the government recognizes the existence of 191 of these settlements, which cause severe ecological damage with the disappearance of trees, advance of urban sprawl, and in some areas, the digging of septic pits. The borough is home to one of the oldest Mesoamerican sites in the valley, Cuicuilco, as well as several major parks and ecological reserves. It is also home to a number of semi-independent “pueblos” that have limited self-rule rights under a legal provision known as “usos y costumbres”.