Puerto Viejo de Sarapiquí — not to be confused with Puerto Viejo de Talamanca on the Caribbean coast — sits where the Sarapiquí and Puerto Viejo rivers meet in the northern lowlands. It was a banana port and the head of river navigation to the Caribbean before the roads came, and it has the slightly left-behind feel of a place that used to matter more.
For visitors it is one of the cheapest places in Costa Rica to see a lot of wildlife. The rivers are run for gentle rafting and for wildlife floats — caiman, sloths, river otters, and birds in quantity — and the private reserves nearby are serious: La Selva, run by the Organization for Tropical Studies, is one of the most-studied patches of lowland rainforest anywhere and takes day visitors with a guide.
It is about ninety minutes from San José over the Braulio Carrillo road, which is itself one of the more dramatic drives in the country.