San Rafael is the largest surviving block of Atlantic forest in Paraguay and the country's most important birding site, with over 400 species recorded. It is also barely a park: the 1992 declaration never came with money to buy the land, so most of it is still privately owned and still being cleared. What protection exists is bought, patrolled and guarded by two NGOs, and Pro Cosara — the Asociación Pro Cordillera San Rafael, run out of Hohenau — is the one you can visit.
Their field site sits on the edge of the reserve in Alto Verá, and the Hostettler family runs the visitor side of it: a pine cabin sleeping nine, a camping area with a proper bathroom, meals either cooked yourself in their kitchen or shared at their table. Four named trails run into the forest from the station — Chachi, Urutaú, Suruku'a sa'yiu and Tuká Pakova — and staff will take you round the reserve by truck or walk the trails with you. There is a nature centre and a lake to swim in.
The thing that makes this reachable without a 4×4 is that they publish the bus. The Pastoreo line leaves Encarnación at 08:00 or 11:30 and Obligado at 09:00 or 12:30, drops you at Ynambú, and somebody comes out the last ten kilometres to fetch you. The bus back passes at one the next afternoon, which tells you the minimum useful stay.
No prices are published and there is no WhatsApp; ring +595 985 710900 or write to Christine Hostettler. Volunteers and researchers are taken on separately through the association.