The Church of the Trinity was built as the result of a vow by Lambach's abbot, when plague was ravaging the whole country in 1713. This promise resulted in the building between 1714 and 1725 of one of Austria's most unusual Baroque sanctuaries. Everything in the church designed by Johann Michael Prunner is symbolic: the circular nave within three chancels, three façades, three portals, three altars, three organs and three sacristies.