The Eastern Hills are a chain of hills forming the eastern natural boundary of the Colombian capital Bogotá. They are part of the Altiplano Cundiboyacense, the high plateau of the Eastern Ranges of the Colombian Andes. The NNW-SSE trending mountain chain is 52 kilometres (32 mi) long and its width varies from 0.4 to 8 kilometres (0.25 to 4.97 mi). Geologically, the Eastern Hills are the result of the westward compression along the Bogotá Fault, that thrusted the Lower Cretaceous rocks onto younger strata. The fold and thrust belt of the Eastern Hills was produced by the Andean orogeny with the main phase of tectonic compression and uplift in the Pliocene. During the Pleistocene, the Eastern Hills were covered by glaciers feeding a large paleolake (Lake Humboldt) that existed on the Bogotá savanna and is represented today by the many wetlands of Bogotá. The main touristic attractions of the Eastern Hills of Bogotá are the Monserrate and Guadalupe Hills. The Eastern Hills were sparsely populated in pre-Columbian times, considered sacred by the indigenous Muisca. The native people constructed temples and shrines in the Eastern Hills and buried their dead there. The Guadalupe and Monserrate Hills were important in their religion and archaeoastronomy, being the hilltops where Sué, the Sun, rises on the December and June solstices respectively, when viewed from the present-day Bolívar Square.