The Danube Islands are formed by river deposits — sand and gravel. Although slowly, the river constantly shapes and changes its banks. This is why the islands are inconstant, they change their area and configuration. The Danube Islands are pieces of paradise, detached from time and the dynamics of modern life. Although the number of Danube Islands exceeds the impressive number of 60, most of them are small in area and importance. An exception to that is Persin Island (Belene) – the largest Bulgarian island on the Danube, followed by Kozloduy, Vardim, Batin, Golyama Barzina, Lyulyak, Aleko and Vetren. The islands of Vardim and Persina (Belene) have reserves due to their bird colonies – white-tailed eagle, eurasian spoonbill, herons, cormorants, as well as the unique Vardim oak.