Los Glaciares, of which 30% is covered by ice, can be divided in two parts, each corresponding with one of the two elongated big lakes partially contained by the Park. Lake Argentino, 1,466 km² and the largest in Argentina, is in the south, while Lake Viedma, 1,100 km², is in the north. Both lakes feed the Santa Cruz River that flows down to Puerto Santa Cruz on the Atlantic. Between the two halves is a non-touristic zone without lakes called Zona Centro.
The northern half consists of part of Viedma Lake, the Viedma Glacier and a few minor glaciers, and a number of mountains very popular among fans of climbing and trekking, including Mount Fitz Roy and Cerro Torre.
The southern part has, as well as a number of smaller ones, the major glaciers which flow into Lake Argentino: Perito Moreno Glacier, Upsala Glacier, and Spegazzini Glacier. Typical excursion boats travel between icebergs to visit Bahía Onelli, and the otherwise inaccessible Spegazzini and Upsala. The Perito Moreno is reachable by land.