To see it all would take years. But on a road trip down Chile’s Route 7—also called the Carretera Austral—you can pack the Patagonian adventures of a lifetime into a two-week journey.

After a day of driving past the Patagonian lakes and forests of the Carretera Austral, I am startled by the sight of a small white cross along the edge of the roadway. Wreathed in wilted flowers ...