The intensive agricultural usage of the soils led to erosion and practically to a destruction of the original vegetation. In the 1930s, the increasing demand for construction areas led Duarte Pacheco, the then Minister for the Public Works of Portugal, to resuscitate an idea from 1868: the reforesting of the then practically bare Serra de Monsanto. The regulation for Monsanto Park was put in place in 1934, and the works for replantation were carried out by farmers and prisoners from Monsanto Fort. Architect Keil do Amaral presented the first complete plan for the park, including leisure and sports areas, some of which still exist. The Ecological Park has a privileged location at Monsanto Forest Park — the largest green patch in the city of Lisbon, with almost 1000 ha. The Monsanto Park Circuit, a 5.44 km (3.38 mi) race track, hosted the 1959 Formula One Portuguese Grand Prix.