Via Gama -Gachalá, descent to the edge of the dam. Guarded by the military at all hours, it is the entrance to the Tunnel, there are about 900 meters that cross the heart of the mountain with an average slope of 10%. Bring lights on and prepare to hear the deafening noise of the buses as they pass by. it is trail, humid and with internal water seepage. It is a UNIQUE AND INCREDIBLE moment !!!