Just 60 km northeast of Posadas is the tiny settlement of San Ignacio, home to the most impressive Jesuit ruins in the province, San Ignacio Mini founded in 1610, now a UNESCO World Heritage Site. The main reason to visit the relatively non-descript town of San Ignacio is the ruins which take up some six blocks at the northeast end of town. The Centro de Interpretacion gives an excellent introduction to life in the missions and there’s a small museum with Jesuit artifacts. San Ignacio Guazu (large) lies on the opposite side of the Rio Parana in Paraguay.

San Ignacio was also once home to the Uruguayan writer Horacio Quiroga and his home surrounded by lush vegetation is now a small museum, the Casa de Horacio Quiroga, which contains many of his belongings. There are a couple of other missions nearby, which include Loreto, once home to some 6,000 people, and Santa Ana, home to over 4,000. Although little remains of the missions besides a few high walls and stone steps.