For several millennia after the end of the last ice age, the Sahara was a grassland with rivers and several massive lakes. (scienceofdoom.com)
Study results which would help to explain the abruptness of the Bølling - Allerød warming, based on observations and simulations, found that 3 ° — 5 °C Ocean warming occurred at intermediate depths in the North Atlantic over several millennia during Heinrich stadial 1 (HS1). (en.wikipedia.org)
After several millennia of existence, the civilization began to break apart for unknown reasons between 600 to 900 A.D., leaving the once - mighty cities to be swallowed up by the jungle. (cahalpech.com)