Catedral de Piria is the unfinished church ruin built by Francisco Piria, the founder of Piriapolis. The Catholic Church never accepted the building, reportedly because of rumours about Piria's links to Freemasonry, and it was left as a strange landmark rather than a working cathedral.
The front remains the most impressive part, with enough structure intact to make the stop worthwhile if you are already exploring Piria's other legacy sites, especially Castillo de Piria and Cerro San Antonio.