Since the orientation of buildings is one of the factors that most strongly influences the development and composition of subaerial biofilms, as it determines the amount of light and the availability of water on the substrate, the role of exposure was also considered by comparing the biodiversity on north and west walls of the three churches. The authors also compared their results with previous work, made on biodiversity on historical granite buildings in urban settings. The results proved that orientation is an important factor regarding both the diversity and abundance of microorganisms on the walls, with environmental factors associated with the north orientation factors favouring a higher diversity. This excellent paper, from [PERSON] et al. [7], also addresses the stone biodiversity topic. In this case the biodiversity of different biocenoses on the historical sandstone of the Northern Pergola in the Museum of King John III's Palace at Wilianow (Poland) are analysed. The authors aimed at describing seasonal changes of microbial community composition in situ in different biocenoses: winter and summer, of the same historical sandstone. Another objective of this work was to describe the seasonal changes of microbial community composition in situ in relation to biodeterioration patterns or with anthropogenic factors, e.g., air pollution. The microbial biodiversity was analyzed by the application of Illumina-based next-generation sequencing methods. The metabarcoding analysis on fungi, bacteria and lichenized fungi are presented and compared between winter and summer. The authors found that the diversity of organisms in the biofilm ensures its stability throughout the year despite the differences recorded between winter and summer. On the other hand, analyses of bacterial and fungal communities' biodiversity in biocenoses from historic sandstone Pergolas revealed that the observed changes were mostly associated with the biodeterioration patterns. This Special Issue also presents four very excellent reviews. In this very interesting work by [PERSON], [PERSON] and [PERSON] [8], the authors review the 21 st century literature (2000 to 2021) regarding the biodiversity and biodeterioration of glass-based historical building materials, particularly stained glass and glazed tiles. These authors study the provenance of the stained glass and glazed tiles with biological colonization, presented in the 21 st century literature. They also compile a list of fungi, bacteria and phototrophic microorganisms reported on glass-based historical building materials and make a critical overview regarding the organism's biodiversity and the colonized materials. They also compare the biodeterioration patterns from case studies with laboratory-based colonization experiments, showing that many deterioration patterns and corrosion products are similar. Finally, the authors make suggestions regarding further studies that are urgent to do in order to fully understand the biodiversity and biodeterioration of stained glass and glazed tiles. In addition, in this special issue, there is an excellent review by [PERSON] and [PERSON] [9] dealing with bioconservation of historic stone buildings. In this review, the authors seek to provide updated information on the innovative bioconversion treatments that have been or are being developed. According to the authors there is an urgent need to replace traditional conservation treatments by more environmentally acceptable, biologically-based, measures, including bioconsolidation and bioceaning. Bioconsolidation can use whole bacterial cells or cell biomolecules while biocleaning can employ microorganisms or their extracted enzymes to remove inorganic and organic surface deposits such as sulphate crusts, animal glues, biofilms and felt tip marker graffiti.