Plainburg Castle - the family seat of the Counts of Plain and a symbol of Großgmain - is one of Austria's oldest castle ruins and offers a magnificent view over Großgmain and the surrounding mountains. All that remains of the original structure are the outside walls, with a thickness of 1.4m and standing to a height of over 5m. A short climb rewards the visitor with the opportunity to stop and rest awhile at the viewing platform overlooking Großgmain. Before it became the seat of the Counts of Plain, the mountain was a Celtic burial ground during the late Bronze Age around 1200 BC. Some time later, in about 1100 AD, Count Werigand of Plain built Plainburg Castle.
References:The Chapel of St. Martin is the only completely preserved Romanesque building in Vyšehrad and one of the oldest in Prague. In was built around 1100 in the eastern part of the fortified outer ward. Between 1100 and 1300, the Rotrunda was surrounded by a cemetery. The building survived the Hussite Wars and was used as the municipal prison of the Town of the Vyšehrad Hill.
During the Thirty Years’ War, it was used as gunpowder storage, from 1700 to 1750, it was renovated and reconsecrated. In 1784, the chapel was closed passed to the military management which kept using it as a warehouseand a cannon-amunition manufacturing facility. In 1841, it was meant to be demolished to give way to the construction of a new road through Vyšehrad. Eventually, only the original western entrance was walled up and replaced with a new one in the sountren side. The dilapidating Rotunda subsequently served as a shelter for the poor.