The great majority of Tz'utujil live either in one of seven municipalidades or in one of the satellite hamlets ( aldeas and caseríos ) surrounding those larger centers. Listed in clockwise order, the Tz'utujil municipalidades lining the shore of Lake Atitlán are San Lucas Tolimán, Santiago Atitlán, San Pedro la Laguna, San Juan la Laguna, and San Pablo la Laguna. In addition Santa María Visitación is situated in the mountains to the west of the lake and Chicacao in the piedmont region to the south. Differing from Guatemala's common "vacant center" towns, in which residents tend to return from more permanent habitations in the surrounding mountains and valleys only on market days and fiestas, Tz'utujil towns are of the "town nucleus" configuration, in which residency is characterized by permanent inhabitation. Until the mid-twentieth century dwellings in most Tz'utujil towns were comprised of a rectangular stone wall of about a meter in height upon which rested a secondary lashed-cane wall extending to ceiling height. The roof of this earthquake-resistant structure was constructed of wooden beams and grass thatch. Although these structures are still to be seen, population pressure and the resulting necessity to construct multistoried dwellings, combined with the new earthquake-resistant materials (particularly cement block and reinforcing steel rods) has led to a revolution in construction techniques.