This is a medieval Russian lay, described as like the Russian Holy Grail story. The link above takes you to Kitezh.com, a site that summarizes the traditional tale and gives examples of Russian organizations inspired by the Kitzeh story.
This is a translation of a bylyni--a nineteenth century term for a much older poetic structure. As a random non-sequitor, folklore is also a nineteenth century term--the things one learns in grad school
This name refers both to a poetic style and, apparently, the longest epic poem composed in burgastica meter in the 15th Century. I could find no online links to The Burgarstica, so the above link takes you to the Codex entry for a recommended print prose translation.