There has been a spa at Alange at least since Roman times when a bathhouse was constructed with separate facilities for men and women. They already existed in the time of Trajan and Adrian, in the 2nd century CE. The Roman building is rectangular and two circular vaulted chambers can be found, one for women and one for men. In the centre of the chambers are the pools, which are also circular. The vaults in the chambers are hemispherical with skylights in the centre. After several centuries of being abandoned, in the 19th century they were refurbished and the current building was built.
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.