In this paper a pioneering, transparent restoration methodology is presented, introducing structural glass elements to substitute missing components of damaged monuments and simultaneously reinforce the original structure. To prove the feasibility of the concept, a damaged medieval tower in Toolse, Estonia is selected as a case study: Soil movements and over-consolidated clay layers result to a widening vertical crack, approximately one meter wide. Alternative designs, with float and cast glass components respectively, are proposed for restoring the crack and improving the wall’s stability. The considerable differences in strength and stiffness between the original wall and the glass addition require connections that establish a coherent system. Specimens bonded with selected adhesives are tested in shear and evaluated. Finally, full-scale prototypes of a characteristic part of the wall are produced and tested in three point bending to compare the overall cooperation and compatibility of each design with the medieval wall.