Concepción is an attractive frontier town on the Río Paraguay in northern Paraguay. It is not really worth a detour in itself, but it is the traditional departure point for river journeys heading upstream toward the Pantanal of Brazil.
The passenger boats that ply the river are primarily freight ships, and travelling on them is an adventure in itself. You will need to bring a hammock to sleep in. The trip is extraordinarily cheap — around five dollars a day on board — but don't expect a cruise-style experience. If you are heading to Brazil (disembarking at Isla Margarita or Porto Murtinho), the lower stretch of the river has limited wildlife. The better sightings are further upstream, from where onward transport to Brazil may or may not materialise.
The town itself has a pleasant riverfront and a quiet, end-of-the-road feel that is characteristic of Paraguay's northern towns. The Mercado Municipal and Plaza Urundé give you the character of the place in an hour's walk.