The present paper describes a specific research performed in the framework of the project “Sustainable Monitoring Techniques for Assessing Instability of Slopes in the Siq of Petra, Jordan” carried out by ISPRA from July 2012 to May 2015. Focus is given to the stability conditions of a large-volume sandstone block located in the northern sector of the Siq, isolated from the rear rock-mass by a sub vertical, partially open, fracture and partially eroded at the base in correspondence of a softer sandstone layer. A limit equilibrium analysis for sliding and toppling failure mechanisms was performed in order to investigate the influence of geometrical and strength parameters and to assess the present stability conditions. These latter were also preliminary evaluated with the support of a numerical analysis, in which the influence of the real geometry and of progressive failure can be studied in detail. This knowledge, associated to the data provided by an integrated monitoring system realised with an automatic and wireless connected crack-gauge network, will help in identifying the most sustainable actions to be realised to mitigate the risk of collapse in such a vulnerable and complex context.