The Ulen Reserve was proclaimed in 1994 to preserve exemplary forest ecosystems developed on silicate rock basis and deposits of rare, endangered and endemic animal and plant species on the land area of Bansko. It covers 3156.2 ha of Pirin NP, of which 2385 ha of the forest fund and 771 ha of the land fund. The purpose of its proclaimantion is to preserve, without human intervention, specimens of forest, subalpine and alpine ecosystems on silicate rock bases, and of rare, threatened and endemic animal and plant species. The Reserve territory is located between 1650 and 2851 m altitude.