There were two Schauenburg castles near Frenkendorf, Alt-Schauenburg about 1 km southwest of the village on the top of Chleiflüeli hill and Neu-Schauenburg to the west. A first castle was probably built for the Lords of Schauenburg in the 11th century, however nothing is known about it. In the 13th century the original castle was replaced by a new castle. The 1356 Basel earthquake destroyed much of it, but unlike Alt-Schauenburg, it was quickly rebuilt. The Schauenburg family became extinct in 1385 and the castle became a fief under the Bishop of Basel. In 1397 it was sold and then over the following centuries passed through several additional owners. However, by the 15th century, it had been abandoned and began to fall into ruin.
By 1480 a group of Beguines lay sisters had occupied the towers of Neu-Schauenburg and established a cloistered house in the ruins. The order remained at Schauenburg until 1523. In 1691 mineral springs were discovered and a bath house was built near the castle ruins. In 1792 a small country estate with attached fields was built near the ruins.
Neu-Schauenburg was built before Alt-Schauenburg, but because Alt-Schauenburg was destroyed and abandoned first, it came to be known as the old castle.
The castle was built on a rocky spur above the valley. It has an irregular floorplan and a gate on the north side with a 2m thick castle wall that follows the edge of the spur. The top of the spur is divided down the center by a narrow band of rock into higher eastern and lower western halves.
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.