Touba is configured as a mandala, or a squaring of the proverbial circle. Its design combines a grid-plan, aligned on the qiblah axis to Mecca, and a wheel, with avenues converging on the Great Mosque, at the center of the scheme. The mandala, or khâtim in Arabic (xaatim in Wolof), is used by Sufis to mark a qutb or the presence of an archetype. In Touba's case, the khâtim urban design is an indicator of the link between the earthly city and its paradisiacal namesake, the tree called Tûbâ.
Touba's khâtim design is most clearly marked on the ground by a circular boulevard, called the Rocade, which confines the holy city and defines it. This Rocade functions at a symbolic level; it sets the holy city apart from a surrounding world which is perceived to be profane. As a holy city, Touba has to be maintained in a state of purity. For Mourides, it is a protected zone, a sacred enclosure from which “Satan and his works” are excluded. It is intended as a holy place which thrives under God's protection. Consequently, forbidden in Touba are all illicit and frivolous pursuits, such as the consumption of alcohol and tobacco, the playing of games, sports, music and dancing.
Touba's immunity from the corruption of the profane world around it is energetically maintained by the Mouride tarîqa. The tarîqa, through its supreme spiritual leader, the Caliph-General, a son and successor of Ahmadou Bamba, maintains absolute control over the holy city, to the exclusion of usual state-run civil and administrative services. Education, health, supply of water, public works, administration of markets, land tenure and real estate development… the tarîqa manages every aspect of the city's life and growth. The tarîqa has even managed to obtain legal recognition from the state of its independent administration of Touba. Since 1976, Touba has had the official status of “autonomous rural community,” though with about half a million inhabitants it definitely qualifies as a city, not a rural place.
In many regards the circular Rocade actualizes Touba's special legal status. It signifies a qualitative break in space, establishing definite precincts for the sanctuary. It is a threshold one must cross on arrival in Touba. Though the city continues to sprawl for many kilometers beyond it, the Rocade serves as a liminal structure, expressing both the holy city's spiritual purity and its political independence.