St Quirinus is the former monastery church of Tegernsee Abbey, the institution that gave the town its shape and much of its prestige. The abbey was founded in the 8th century and later became one of Bavaria's important Benedictine centres; the church you see now carries a bright Baroque interior over much older religious foundations.
The setting is half the pleasure. The church stands in the former monastery and castle complex right by the lake, with the brewery, Bräustüberl, and waterfront close by. It is the best place to understand Tegernsee as more than a pretty lakeside resort.