Mearns Castle was built by Herbert, Lord Maxwell, under a royal warrant issued in 1449, and remained with the family until James VI required the fifth Lord to deliver it up to the crown. It was sold to Sir George Maxwell of Nether Mearns in the mid-17th century, and later passed to the Shaw-Stewart family. In 1971 the tower's remaining stories were converted to a link between two Church of Scotland buildings.
The castle was originally a four-storey rectangular tower measuring 9.1 by 12.2 m; parts of the original corbelling remain. Its lower walls are rubble masonry up to a height of about 10 feet, the upper walls are constructed from well-cut ashlar blocks, demonstrating that the tower was probably built on the foundations of an earlier building. The arched main entrance on the first storey was reached by a ladder, but is now walled up.
Only faint traces of the castle's outerworks can be located. A barmkin followed the edges of the rocky knoll on which the building stands and the sloping ground on the southeast has been cut away to form a bank approximately 10 feet high, over which a causeway led to the tower's gatehouse.
There is a vaulted basement room, approached from the main entrance. The first-floor hall, which is also vaulted, is approached by a straight mural stair; it has stone window seats and once had a minstrels’ gallery.
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.