Marrakesh is possibly the most important of Morocco's four former imperial cities. The region has been inhabited by Berber farmers since Neolithic times, but the actual city was founded in 1062 by Abu Bakr ibn Umar. In the 12th century, the Almoravids built many madrasas (Koranic schools) and mosques in Marrakesh that bear Andalusian influences. The red walls of the city, built by Ali ibn Yusuf in 1122–1123, and various buildings constructed in red sandstone during this period, have given the city the nickname of the "Red City" or "Ochre City". Marrakesh grew rapidly and established itself as a cultural, religious, and trading center for the Maghreb and sub-Saharan Africa; Jemaa el-Fnaa is the busiest square in Africa. In 2009, Marrakesh mayor Fatima Zahra Mansouri became the second woman to be elected mayor in Morocco. Like many Moroccan cities, Marrakesh comprises an old fortified city packed with vendors and their stalls (the medina, a UNESCO World Heritage Site), bordered by modern neighborhoods, the most prominent of which is Gueliz. Today it is one of the busiest cities in Africa and serves as a major economic center and tourist destination.