Drone footage shows rocky islands and debris dotting the surface of Poland's longest river, as experts said water levels had reached a historic low.<br /><br />Levels in the Vistula River dropped to 25cm, beating a record set during a drought in 2015 – and the short-term forecast suggests the water level will drop further this week.<br /><br />The Vistula is Poland's longest river, rising in the mountains close to the Czech border and flowing for more than 1,000km to the Baltic Sea.<br />
