Llamas, Photo courtesy of Media for the Arts		1 of 3   Middle Horizon
	MIDDLE HORIZON A.D. 600-A.D. 900 ower shifted from coastal areas to the southern highlands where the first Andean empires, Tiwanaku and Huari, appeared. Experience in exploiting the vertical ecology of the highlands gave these civilizations the organizational and technological skills needed to link diverse zones and peoples under a central authority. Local regions were integrated into the national economy through a system of state-built irrigated terraces, buildings, and roads. Llama caravans were used for vast trade networks and state agents were stationed throughout the empires to assure cohesive rule.