At Palmar, travellers heading south face a choice: most people intent on the quickest route to Panamá stick to the Interamericana, which heads south for the final 100km to Panamá. This section of the trip down to the Paso Canoas border crossing is through an empty featureless, frontier region, with the refuelling point of Ciudad Neily the only point of minor interest.
The alternative route is to head east along the Interamericana, which switchbacks its way to the small, sleepy town of Paso Real, 20km away, following the wide and fast-running Río Grande de Térraba as it cuts a giant path through the almost unbearably hot lowland landscape, its banks coloured red with tropical soils. Rainstorms seem to steamroller in with the express purpose of washing everything away, and you can almost see the river rise with each fresh torrent. This stretch is prone to landslides in the rainy season, when you can find yourself stranded by a sea of mud.
At Paso Real, you can pick up the paved Hwy-237, which takes you south through some spectacularly scenic country. Steep and winding, with beautiful views, it is little used by tourists except those few heading to the pretty mountain town of San Vito, the jumping-off point for the Wilson Botanical Gardens, Parque Internacional La Amistad and the Río Serena border crossing.