At the time of the conquest, the Eastern Hills were a forested natural boundary of the Bogotá savanna. During the early colonial period, the Spanish constructed a cross on Guadalupe Hill as a symbol to protect the capital of the New Kingdom of Granada. The wood of the trees of the Eastern Hills were used for construction and heating in the city that grew steadily until the 19th century. This led to deforestation and erosion in the Eastern Hills and when Alexander von Humboldt visited Santa Fe de Bogotá in 1806, he noted that there was not a single tree left until the open area of Choachí. The first replanting of trees took place in 1855, and a second phase of reforestation happened in 1940. In 1801, Francisco José de Caldas recalculated the height of Guadalupe Hill.