To visit the beautiful Glaciar Perito Moreno it's the most convenient to book a tour in El Calafate. This glacier grows directly into a side branch of Lago Argentina (Brazo Rico) and builds a natural barrier for the southern part of that branch, which dames up the water up to 18m. Every five to seven years (used to be three to four, when global temperatures were a little lower), the pressure of the water causes the dam to break. The glaciers front is a wall of ice of 60m height and is around 4km wide. Often huge pieces of ice thunderous fall down into the water, drifting away as icebergs.