A delightfully-accessible 13th-century fortress that now lies in ruins above Bosanska Krupa, this should be your first stop when in town. There isn’t a huge amount to see within the ruins (they are ruins, after all), but that intangible sense of history that only decrepitude can create is most certainly here. The views are stunning too, extending over both side of the city with the rivers playing a starring role. The fortress was originally in Croatian hands, although it eventually fell to the Ottomans in the 16th century, at which point the town began to grow. The Ottomans were sure to keep this spot well-stocked, as it was an important stronghold for their ambitions to spread west, although it never really worked out for them in that respect. This is history, intangible history, with added beauty.
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.