Nendrum Monastery may have been founded in the 5th century, but this is uncertain. The monastery came to an end at some time between 974 and 1178, but its church served a parish until the site was abandoned in the 15th century. Some remains of the monastery can still be seen.
Dendrochronology has dated a tide mill on the island to the year 619, making this the oldest excavated tide mill anywhere in the world. The monastic site included orchards, gardens, pastures, arable fields, and a guest-house.
The principal monastic remains which can now be seen are three concentric cashels (enclosures) of dry stone walling, but these were substantially rebuilt by Lawlor in the 1920s. The central cashel has the round tower remains, a ruined church with a sun-dial, and a graveyard. The second cashel contains what is called a 'monastic school' or workshop and other burials.
The canonical sundial now seen at one corner of the ruined church was reconstructed from fragments found during the excavation of the site in 1924 and has been dated to about the year 900. One of only a few early medieval sun-dials known to exist, it takes the form of a vertical stone pillar, 190 cm high, 40 cm wide and 15 cm thick, with the dial and gnomon on one face at the top. However, because of the nature of the reconstruction, the original height of the pillar is conjectural.
The Holy Trinity Column in Olomouc is a Baroque monument built in 1716–1754 in honour of God. The main purpose was a spectacular celebration of Catholic Church and faith, partly caused by feeling of gratitude for ending a plague, which struck Moravia between 1713 and 1715. The column was also understood to be an expression of local patriotism, since all artists and master craftsmen working on this monument were Olomouc citizens, and almost all depicted saints were connected with the city of Olomouc in some way. The column is the biggest Baroque sculptural group in the Czech Republic. In 2000 it was inscribed on the UNESCO World Heritage Sites list.
The column is dominated by gilded copper sculptures of the Holy Trinity accompanied by the Archangel Gabriel on the top and the Assumption of the Virgin beneath it.
The base of the column, in three levels, is surrounded by 18 more stone sculptures of saints and 14 reliefs in elaborate cartouches. At the uppermost stage are saints connected with Jesus’ earth life – his mother’s parents St. Anne and St. Joachim, his foster-father St. Joseph, and St. John the Baptist, who was preparing his coming – who are accompanied by St. Lawrence and St. Jerome, saints to whom the chapel in the Olomouc town hall was dedicated. Three reliefs represent the Three theological virtues Faith, Hope, and Love.
Below them, the second stage is dedicated to Moravian saints St. Cyril and St. Methodius, who came to Great Moravia to spread Christianity in 863, St. Blaise, in whose name one of the main Olomouc churches is consecrated, and patrons of neighbouring Bohemia St. Adalbert of Prague and St. John of Nepomuk, whose following was very strong there as well.
In the lowest stage one can see the figures of an Austrian patron St. Maurice and a Bohemian patron St. Wenceslas, in whose names two important Olomouc churches were consecrated, another Austrian patron St. Florian, who was also viewed as a protector against various disasters, especially fire, St. John of Capistrano, who used to preach in Olomouc, St. Anthony of Padua, a member of the Franciscan Order, which owned an important monastery in Olomouc, and St. Aloysius Gonzaga, a patron of students. His sculpture showed that Olomouc was very proud of its university. Reliefs of all twelve apostles are placed among these sculptures.
The column also houses a small chapel inside with reliefs depicting Cain's offering from his crop, Abel's offering of firstlings of his flock, Noah's first burnt offering after the Flood, Abraham's offering of Isaac and of a lamb, and Jesus' death. The cities of Jerusalem and Olomouc can be seen in the background of the last mentioned relief.