The most famous of all the reducciones, San Ignacio Miní (daily 7am–7pm) was originally founded in 1610 in the Guayrá region, in what is now Brazil. After the bandeirantes attacked the mission in 1631, the Jesuits moved thousands of miles southwards through the jungle, stopping several times en route at various temporary settlements before finally re-establishing the reducción at its present site in 1696.
The ruins occupy six blocks at the northeastern end of the village of San Ignacio: from the bus stop head east along Avenida Sarmiento for two blocks and turn left onto Rivadavia. Follow Rivadavia, which skirts around the ruins, for six blocks and then turn right onto Alberdi, where you’ll find the entrance to the site. At the entrance, there’s a small but worthwhile museum with a series of themed rooms depicting various aspects of Guaraní and mission life, plus a detailed maquette of the entire reducción. The site itself is dotted with panels lending context to the ruins, with audio provided in various languages, including English. Free, more detailed tours in rapid-fire Spanish depart regularly from the museum. There are also popular sound and light shows each evening.