Additive manufacturing (AM) allows production of highly complex, resource-efficient and high accuracy objects, without the need of moulds or other tools for shaping, based on a three-dimensional CAD model. Application of 3D printing in the field of cultural heritage restoration, is a promising approach to recreate artworks elements. The aim of this work is to evaluate the applicability of 3D printing technologies for the realization of structural/decorative elements that integrate gaps in the architectural heritage, in order to preserve and/or make it usable, while respecting the reversibility, durability and distinguishability of the materials. The main advantages of 3D printing over the use of traditional technologies are the possibility of reproducing elements of any geometry, even complex ones; the attractive weight—mechanical performance ratio, which is particularly important for historical buildings in seismic areas; the reduction in time required for the restoration work. In detail, a case study is herein considered. It refers to the reconstruction of the window cornices of the historical building Palazzo Orsini originally located in the central Italy. They are reproduced exploiting a particular 3D printing technique, i.e. the powder bed fusion. All the stages of this process are described and discussed. The idea is to use the faithful 3D reproductions of the cornices on the reconstructed building as they are lighter than the original ones, which could thus be preserved in a museum. The final aim of this project is the definition of an innovative design and production process for the realisation of decorative elements for the integration of architectural gaps necessary to recover an architectural asset.