Berezan Island. Map: VII-12. Island in the Black Sea at the Dnieper-Boh Estuary, 850 m in length, 200–850 m in width. This was the site of the oldest Greek (Ionian) colony in southern Ukraine, founded in the second half of the 7th century BC. Called Borysthen or Borysthenida, it existed until Roman times. During the period of Kyivan Rus’ there was a Slavic settlement at Berezan Island. The Zaporozhian Cossacks used it as a fortress during their campaigns against Turkish settlements.