With the prevalence of asthma increasing worldwide in recent decades there is a growing need to determine the diversity and spatiotemporal dynamics of airborne microbes in indoor environments. Hence, the aims of this study were to detect and identify fungi present in public heritage buildings (libraries, museums, churches) in Poland. Samples of indoor dust and biofilm were collected from 60 areas in 10 such buildings (mostly in urban environments) in different seasons in 2008-2011. Mycological analysis was based on the culture-dependent method using 2% MEA and SNA. In 300 samples there were at least 160 fungal species belonging to more than 70 genera. The most common were Acremonium, Alternaria, Arthrinium, Aspergillus, Aureobasidium, Botrytis, Chaetomium, Cladosporium, Fusarium, Monodictys, Mucor, Nectria, Oidiodendron, Penicillium, Phoma, Rhizopus, Sarocladium, Simplicillium, Scopulariopsis, Talaromyces, Trichoderma and Tritirachium. Apart from filamentous fungi and yeasts (Candida and Sporobolomyces), single species of Oomycota (Pythium insidiosum), Actinobacteria and Myxogastia were detected. Most of the taxa recorded have been regarded as important indoor contaminants. Potential health hazards and the deterioration of contaminated objects are discussed.