The Blue Nile Abbai, but pronounced transliterated: an-Nīl al-Āzraq) is a river originating at Lake Tana in Ethiopia. With the White Nile, the river is one of the two major tributaries of the Nile. The upper reaches of the river is called the Abbay in Ethiopia, where it is considered holy by many, and is believed to be the Gihonriver mentioned as flowing out of the Garden of Eden in Genesis 2.

The Blue Nile Falls which are also known as the ‘’Tis Issat’’ are a waterfall on the Blue Nile river in Ethiopia. They are known as in Amharic, when translated, means "smoking water" They are situated on the upper course of the river, about 30 kilometers downstream from the town of Bahir Dar and Lake Tana.

The falls are estimated to be between 37 and 45 meters high, consisting of four streams that originally varied from a trickle in the dry season to over 400 meters wide in the rainy season. A short distance further downstream sits the first stone bridge constructed in Ethiopia, built at the command of Emperor Susenyos in 1626. According to Manoel de Almeida, stone for making lime had been found nearby along the tributary Alata, and a craftsman who had come from India with Alfonso Mendez, the Catholic Patriarch of Ethiopia supervised the construction.