Kovachevsko kale was a Roman city which lies 6 kilometres west of the Bulgarian town of Popovo. The Czech archaeologist Karel Škorpil called it Kovachoveshko kale, after the name of the nearby village, Kovachevets.
It is notable for its massive defensive walls which have a roughly triangular plan and enclosed an area of more than 40 hectares. The stone walls are fortified with 17 U-shaped towers. There are two gates, one to the west and one to the north-east.
The city is located on a flat terrain, naturally protected by rivers.
The strong 3.20 m thick walls were built between 308 and 324 AD during the joint reign of Roman Emperors Constantine I the Great and Licinius after the Gothic Wars of 250-269. The city was set on fire in the Second Gothic War of 376-382 AD. It was slowly restored until the invasion of Attila the Hun around 447 AD. Finally it was destroyed by the Slavs and Avars in the 580s.
Recent excavations by Veliko Tarnovo University have revealed a huge Roman building from the 4th century AD within the walls which appears to have been a horreum (i.e. a granary). It measured over 60m x 25m, though it has not been fully exposed. It had a massive double door of 2.4m width. The walls of the building are 1.3m wide reinforced with external buttresses. It had two stories and a basement and was constructed with opus mixtum. The granary was plundered and set on fire around 378 AD probably by the Goths.
An underground aqueduct built of clay pipes supplied the fortress with drinking water, descending from the northwest over several kilometres from Kalakoch hill.
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.