The Castle of Cabra was raised, within the walled enclosure in the North West of the present town, on a spot high enough to overlook the whole town. It is said that it had a central square surrounded by a strong wall with eighteen towers where eight or ten thousand men could march. At present, most of what remains, it is enclosed within the constructions of the present School of the Escolapias. Among the constructions we have been able to locate the wall, of which something more than half still remains and to track the rest until we were able to determine, quite accurately, the plant of the enclosure which must have been quadrangular, of about 76x47m. The thickness of the walls is about two meters and sixty centimetres, approximately. The fact that the rest of the walls- and possibly of towers are surrounded by modern constructions hinders their thorough study.
As far as the towers are concerned, we can say that two of them are well known, plus the location of other two, that were to the sides of the present front door to the enclosure. In the centre of the East wall and half way out is the tower of Homage. It is almost square shaped and it is more than twenty meters high. At about eleven meter above ground level there is a squared chamber with an eight sided vault ceiling with tubes in the angles. The other tower is located in the northwest angle. It is of squared plant, with the angle that looks to the interior of the chamfered enclosure. The lower part is massive and in the upper part there is a chamber with a barrel vault. It still keeps about ten meters of its height and its maximum surface on the plant is 6.5×6.3m.
Of the other two acknowledged towers there only remain their foundations upon which modern constructions have risen.
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.