In the prehistoric age on the hill of San Giusto there was a castelliere (fortified borough), which in the Roman age became an important urban centre. The fortress, built by the Venetians in the Middle Ages, was pulled down in the 14th century by will of the Patriarch of Aquileia and, in 1470 only, it was rebuilt by Friedrich II of Habsburg; the square tower and the two-storey building, which today houses the Castle Museum, date back to this period.
Under the rule of the Republic of Venice, which at the beginning of the 16th century had re-established its rule over Trieste, the castle's defences were strengthened and, under the Austrian rule again, the works continued until the building, in 1630, of the large ramparts and of the linking walls.
The fortified complex can be accessed from a ramp ending in a wooden drawbridge, over a not very wide moat; after crossing the cross-vaulted hall, you will reach the Piazzale delle Milizie (Square of the Troops), where stairs and allures lead to the ramparts.Since 1930 the castle has been a property of the Municipality, which has equipped it for tourist purposes and uses it for cultural events, shows and temporary exhibitions.
Since 2001 the Lalio rampart of the Castle of San Giusto has been housing the new Lapidario Tergestino, which preserves all the Roman stone finds that were previously displayed in the Orto Lapidario garden.
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.