The area of modern Bogotá was first populated by groups of indigenous people who migrated south based on the relation with the other Chibcha languages; the Bogotá savanna was the southernmost Chibcha-speaking group that exists from Nicaragua to the Andes in Colombia. The civilization built by the Muisca, who settled in the valleys and fertile highlands of and surrounding the Altiplano Cundiboyacense (modern-day departments of Cundinamarca and Boyacá and small parts of Santander), was one of the great civilizations in the Americas. The name Muisca Confederation has been given to a loose egalitarian society of various chiefs (''caciques'') who lived in small settlements of maximum 100 ''bohíos''. The agriculture and salt-based society of the people was rich in goldworking, trade and mummification. The religion of the Muisca consisted of various gods, mostly related to natural phenomena as the Sun (Sué) and his wife, the Moon; Chía, rain Chibchacum, rainbow Cuchavira and with building and feasting (Nencatacoa) and wisdom (Bochica). Their complex luni-solar calendar, deciphered by Manuel Izquierdo based on work by Duquesne, followed three different sets of years, where the sidereal and synodic months were represented. Their astronomical knowledge is represented in one of the few extant landmarks of the architecture of the Muisca in ''El Infiernito'' outside Villa de Leyva to the north of Bogotá.