From Lago Viedma’s north shore, south of El Chaltén, the park’s best lake excursion is the catamaran Viedma Discovery’s full-day voyage to the Viedma glacier, which includes an ice-climbing component.

Sailing from Bahía Túnel, the vessel rounds the ironically named Cabo de Hornos (Cape Horn) to enter an iceberg-cluttered area before anchoring in a rocky cove. After disembarking, visitors hike to an overlook of the glacier (Argentina’s largest, though its lakeside face is small) and of 2,677-meter Cerro Huemul. Those who wish can strap on crampons and continue onto the glacier for about 1.5 hours (even some pretty sedentary porteños do so).

The bilingual guides know glaciology and provide more personalized service than the Fernández Campbell excursion from Puerto Bandera. While the price here does not include lunch, they do provide an aperitif on the glacial rocks.

Departure time from El Chaltén is 8:30 a.m., while the boat sails from Bahía Túnel at 9 a.m.; the cost is US$50 per person plus US$6.50 for transportation from El Chaltén for those who need it. For details, contact Viedma Discovery (Güemes s/n, tel. 02962/493110, El Chaltén).

Formerly just a restaurant, Bahía Túnel (tel. 02962/493043, US$73 d) now has three guest rooms that share a bath. The restaurant is still a good breakfast choice, with exceptional picture-window views across the lake. It also serves lunch, afternoon tea, and a sunset dinner which is ideal for views over the lake.