Nera (Danube) basin and it is not navigable. After the filling of the artificial Lake Đerdap, as a result of the Iron Gate I Hydroelectric Power Station which was finished in 1972, the mouth of the river into the Danube was flooded. In order to allow the optimal electricity production, the water level of the Nera at the mouth should not go below , while it must not exceed it if the flooding of the banks is to be avoided. Since the mid-1990s, there are significant problems in fixing the river's level, as the process is costly and complicated. In 2018, representatives
Enns (town) Leopold V. Following the death of Ottokar IV in 1192, his Duchy of Styria — then significantly bigger than the contemporary state, reaching from present day Slovenia to Upper Austria — fell to the House of Babenberg. Thus, Enns became Austrian. As Leopold VI, Duke of Austria, endowed Enns with town privileges in 1212, it is now considered Austria's oldest town (apart from the Roman municipal status). The landmark of Enns, the belfry (Town Tower) on the Main Square, was erected between 1564 and 1568 as a bell tower, watch and clock tower during the reign of emperor Maximilian II.