The Church of St Nicholas is a parish church dating from the 13th century. Its exceptional size reflects the importance and standing of the borough of Grosmont at the time of the church's construction and has led it to be called a 'miniature cathedral'.
By the late 19th century the church was close to collapse and was saved through an extensive reconstruction in 1869–79 by J. P. Seddon.
The church is built of Old Red Sandstone with ashlar dressings and slate roofs. It comprises the nave, transepts, the central tower, a chancel, a secondary chapel and a porch.
Largely unaltered from the time of its building, by the 19th century the church had seriously decayed and its tower was close to collapse. It was rescued from dereliction in a restoration.
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.