The hill where the Jumilla castle is built was inhabited by people from the Bronze Age. In a later era, this was occupied by people when Iberian civilizations were present in large part of Iberian Peninsula, and specifically in the current municipality. In Roman Iberian Peninsula period, people also leveraged this hill. The last era in regards to this hill before the construction of the current castle is the one when large part of Iberian Peninsula was under Muslim peoples rule. They built a fortress in the 8th century, but they used unstable materials.
In 1241 Jumilla Castle was conquered by troops of Ferdinand III of Castile. Around 1290 the area passed to the Kingdom of Aragon. In 1357 the castle was taken by Ferdinand of Aragon, who had sided with Peter of Castile. Shortly after, Ferdinand again pledged his obedience to his brother, Peter IV of Aragon. Thus the castle returned to the Aragonese crown. In 1358 the castle was again taken for the Castilian crown by Fadrique Alonso, Lord of Haro and Master of the Order of Santiago.
The current castle was built in the year 1461 and its architectural style is gothic.
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.