Reichenau, called AUGIA DIVES in medieval Latin MSS. and possessing a once celebrated Benedictine monastery, is an island upon the Gnadensee (Untersee) of the Lake of Constance, about one mile in breadth and about three and three-quarter miles long. It belongs to Baden, and has 1600 Catholic inhabitants, principally vintagers and fishermen, distributed among three villages, Oberzell, Mittelzell, and Unterzell (or Niederzell). Since 1838 the island has been connected with the mainland by a dam one and a quarter miles in length, and with the railroad station of Reichenau (via Constance). There is a calling station for steamers on the southern shore. The word “Zell” (cell) n the names of the three villages of Reichenau indicates the existence of a monastery on the island, which was the “reiche e” (the fertile islet) of medieval culture. Under the protection and at the suggestion of Charles Mantel, the Anglo-Saxon (?), Saint Pirmin founded, with the cooperation of Count Berthold and the Alemannian Duke Santfrid I (Nebi), the famous Benedictine monastery of Reichenau, which in earlier times, until the tenth century, bore the name of Sintleosesau (Sintlas Ow). Reichenau had attained its full glory when the Abbey of St. Gall was still comparatively unimportant. In spite of St. Pirmin’s banishment from his monastery through the political machinations of the Alemannian prince, Reichenau soon recovered its importance. His immediate successor, Abbot Heddo (727-34), later Bishop of Strasburg, shared the fate of the founder. The growth of Reichenau was greatly fostered by its position on the highway to Italy, which was frequented by Greek and Italian, and even Irish and Icelandic pilgrims and wayfarers. These became guests at the monastery and enriched it with gifts of precious relics, some of which are still preserved in the church treasury. Among other relics was one of special value, a cross with the blood of Christ, which was said to have been brought by an Arabian named Hassan to Charlemagne, and to have been confided to the custody of Reichenau in 925. The monastery also gloried in the possession of relics of St. Mark, brought to Reichenau from Venice in 830. On his homeward journey from St. Maurice with the relics of St. Maurice and other saints, Bishop Ulrich of Augsburg stayed at Reichenau, and, at the petition of Abbot Alewich (934-58), gave a large portion of the relics of Saint Maurice to the monastery [cf. Schmid, “St. Ulrich, Bischof von Augsburg (890-973)”, Augsburg, 1901, p. 281. Bishop Egino of Verona resided in Reichenau, and built (799) the parish church of St. Peter at Niederzell, a small Roman basilica with two towers, whither he retired to lead the life of a hermit, dying in 802. His monument still exists. The property of the monastery was composed principally of donations made by Charlemagne, Louis the Pious, Charles the Fat (who is interred at Reichenau in the monastery church of Mittelzell), and many other German kings and emperors, especially of the House of Otto. The consequence of these royal favors was the rapid growth of the monastery in importance, being granted successively immunity from secular authority, jurisdictio fori the status of a principality of the empire, and complete exemption from episcopal jurisdiction.
Reichenau displayed its greatest lustre in the first centuries after its foundation (especially between the ninth and the middle of the thirteenth centuries), during which it discharged its great work of civilization. The men most prominent for scholarship and ability during this period labored at Reichenau e.g. Walfrid Strabo (839-49); Hatto (891-913), from 891 Archbishop of Mainz; Berno (1008-48), appointed by Emperor Henry II successor of the uncultured Abbot Immo, who had been thrust upon the monastery by the same emperor; St. Meinrad (Meynrad), Count of Zollern (d. 861), the hermit and founder of Maria-Einsiedeln, who came from the monastery of Reichenau; moreover, Hermann Contractus (d. 1054), the acute scholar and historiographer, author of the Salve Regina. The last was a relative of St. Ulrich. These and other scholars labored at Reichenau and formed the famous Reichenau library and school of painters (Codex Egberti). The Reichenau school of painting is seen at its best even today in the single extant work of the tenth century—the eight pictures on the upper part of the walls of the little Roman basilican parish church (St. Georgskirche) at Oberzell—and in the paintings on the walls of the church of St. Peter at Niederzell, which belong to the first half of the eleventh century, and were discovered by Kiinstle and Begerle in 1901 (consult Kiinstle, “Die Kunst des Klosters Reichenau im IX. and X. Jahrhundert,” Freiburg, 1906). As a consequence of its prosperity, laxity and decay came upon the monastery, and caused its incorporation with the Diocese of Constance in 1541. The bishops of Constance thus became commendatory abbots, and the personnel of the monastery was reduced to twelve monks (inclusive of the prior) and a small number of novices. In 1757 the few remaining monks were forcibly removed to other monasteries, and the novitiate abolished. Members of neighboring monasteries performed the religious services at Reichenau until the monastery was secularized in 1802.