Abstract An unexpected and instantaneous slide of rock mass from escarpment of a side cut, and which had already been partly remedied, occurred on the road Jablanica—Prozor/Rama near Mary's cave. The entire rock mass on the studied site is divided into individual blocks in the form of vertical columns and prisms. The main rock mass rests on primary fractures with a gradient of 30–80, which corresponds to limit angles of friction in cracks with similar fills, so there is a danger of new slides. Geotechnical investigations, which consisted of geological engineering works and geotechnical analyses, were performed on the site. The aim of investigations was to establish engineering-geological characteristics of the examined slope, reasons of instability, and to propose rehabilitation measures on the analyzed location.