In 1st and 2nd century, the remains of a Roman temple are dated, broken during Alamannic occupation of the Swiss plateau. In 5th or 6th century, a first Christian church was built on this probably pre-Roman sacred area. Ufenau is first mentioned in 741 as «Hupinauia», and in 744 as «Ubinauvia» – island of Huppan or Huphan. Probably between 900 and 920, the early Christian church was destroyed by the Huns. On 23 January 965, the island was given by Emperor Otto I to Einsiedeln Abbey, that still is its owner. In 926 or some years later, St. Peter & Paul church' preceding building was given by the Hunfridings noblewoman Reginlinda and Burchard II, Duke of Swabia, in addition with a house for herself and her son Adalrich. Reginlinda died in 958 and is buried in Einsiedeln. In 973 later Saint Adalrich (Canonization in 1659) died on Ufenau.
