During centuries, fortification walls and towers were built to protect ancient Nessebar. The first inhabitants on the peninsula were the Thracians who started to build these walls in the 8th century BC. From this period, a fortified wall and gate were found and can be seen today. After the decay of the Roman Empire, Byzantine rulers started an active construction work in the middle of the 5th century AD. The built walls were in style opus mixtum- an alternation of bricks and stone. Best preserved walls can be seen today near the city gate. The early Byzantine construction system was used in the middle ages as well.
Due to enemy war attacks, part of the walls were destroyed, but then quickly rebuilt. After the Ottoman rule in 1453, the fortification walls lost their significance and strategic importance and were left in ruins.
References:Rosenborg Palace was built in the period 1606-34 as Christian IV’s summerhouse just outside the ramparts of Copenhagen. Christian IV was very fond of the palace and often stayed at the castle when he resided in Copenhagen, and it was here that he died in 1648. After his death, the palace passed to his son King Frederik III, who together with his queen, Sophie Amalie, carried out several types of modernisation.
The last king who used the place as a residence was Frederik IV, and around 1720, Rosenborg was abandoned in favor of Frederiksborg Palace.Through the 1700s, considerable art treasures were collected at Rosenborg Castle, among other things items from the estates of deceased royalty and from Christiansborg after the fire there in 1794.
Soon the idea of a museum arose, and that was realised in 1833, which is The Royal Danish Collection’s official year of establishment.