Collegiate Church of the Holy Cross and St. Bartholomew is one of Ostrów Tumski's most beautiful and iconic structures, thanks to a 70m steeple and impressive entry staircase, this curious sanctuary is actually two churches in one. Split over two levels, the building comprises the shorter windows of the Church of St. Bartholomew beneath the soaring windows of the upper level Church of the Holy Cross. The first two-storey church in Silesia, and one of only a few in all of Europe, the church was completed in 1295 as an act of reconciliation ending a long dispute between Duke Henry IV and Bishop Thomas II. For centuries the sarcophagus of Henry IV was housed in the upper Church of the Holy Cross, however today it can be seen on display in the National Museum. Standing outside the church is a large sculpture of John of Nepomuk dating from 1732.
References:The Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.