The Olmec heartland is the southern portion of Mexico's Gulf Coast region between the Tuxtla mountains and the Olmec archaeological site of La Venta, extending roughly 80 km (50 mi) inland from the Gulf of Mexico coastline at its deepest. It is today, as it was during the height of the Olmec civilization, a tropical lowland forest environment, crossed by meandering rivers. The major heartland sites are: * San Lorenzo Tenochtitlán * La Venta * Tres Zapotes * Laguna de los Cerros - the least researched and least important of the major sites. Smaller sites include: