Named for the priest who spearheaded the Salesian evangelism among the Selknam, this elongated water body fills a structural depression that stretches across the Chilean border to the west. Also known by its Selknam name, Kami, its shoreline is nearly 200 kilometers long and its surface covers nearly 600 square kilometers.

The lake’s most westerly part, along the Chilean border, lies within Parque Nacional Tierra del Fuego but is accessible only by boat. As might be expected, the lake is popular with fishing enthusiasts.

Since the closure of Hostería Kaikén at the east end of the lake, the main accommodations this side of Ushuaia are at Lago Escondido’s Hostería Petrel (Ruta Nacional 3, Km 3186, tel. 02901/433569, petrel [at] arnet [dot] com [dot] ar, US$47 d), which has lake-view rooms with Jacuzzis and a restaurant that serves tour groups.

At the east end, about midway between Río Grande and Ushuaia, pilgrims pause at Tolhuin to sample the goods at Panadería la Unión (www.panaderialaunion.com), a legendary bakery. It has the usual fine bread but also loads of facturas (pastries), alfajores, and sandwiches. What it lacks, astonishingly for Argentina, is espresso—settle for machine-dispensed instant.

For a full meal, there’s nearby La Posada de los Ramírez (Av. de los Shelk’nam 411, tel. 02901/492382), which has excellent pastas at bargain prices as well as meats and, on occasion, local specialties such as trout.