The Saint John Abbey Mustair is a Benedictine monastery located in the village of Mustair in the Swiss canton of Graubünden. The monastery is a UNESCO World Heritage Site and is one of the most important cultural and historical landmarks in the region.

The abbey was founded in the 8th century and is renowned for its well-preserved medieval architecture and artwork. The abbey church, which dates back to the 9th century, is considered one of the most important examples of Carolingian architecture in the world. The church features stunning frescoes that cover the walls and ceiling and are considered some of the best-preserved examples of medieval frescoes in Europe.

In addition to its impressive church, the Saint John Abbey Mustair is home to a large collection of manuscripts and other artifacts that provide insight into the religious and cultural history of the region. The monastery also has a rich musical tradition and is known for its performances of Gregorian chant and other sacred music.

The abbey is still home to a community of Benedictine monks who live and work on the grounds. Visitors to the abbey can take guided tours of the church and monastery, attend religious services, and explore the surrounding landscape, which includes hiking trails and stunning mountain vistas.