The diabase (Silurian basalt) rocks of Motol (W part of Prague) are a well-known locality among lichenologists, having been studied for almost 200 years. The oldest published record of a lichen from the area dates back to 1827 (by P. M. Opiz). The locality is also the locus classicus of several saxicolous lichen taxa, mainly forms and one species. This article summarises historical records from Kalvárie v Motole Nature Monument (3.65 ha) and presents detailed results of the recent diversity. We report here 222 lichen taxa, seven lichenicolous and five non-lichenised fungi. An additional 18 lichens are known solely from historical records. Within Prague, it is an exceptionally rich and valuable area. This is underlined by the occurrence of many rare species. Lepraria bergensis is reported here as new to the Czech Republic. Its distinction and relationship with L. borealis are briefly discussed. The lichenicolous fungus Erythricium aurantiacum is published here as new to the country. Cladonia krogiana was found at its second locality in the country, Lecanora stenotropa at its third one. Crustose cyanolichen Lichinella sp. represents a potentially undescribed species. Caloplaca arcis, C. crenularia, Cladonia peziziformis, C. polycarpoides, Immersaria athroocarpa, Peltigera ponojensis, Pertusaria amarescens, Pleopsidium flavum, Porocyphus rehmicus, Psilolechia leprosa, and Verrucaria sphaerospora represent other remarkable records. Saxicolous communities on diabase are dominated by a subset of basiphilous lichens on volcanic rocks, supplemented by species typical of calcareous substrates. The basaltic rocks are locally enriched with metallic ions and these sites host a specific community dominated by two Stereocaulon species. Terricolous communities are only locally developed, but rich in Cladonia species. Epiphytes are especially common in sunny places and dominated by nitrophilous species. The forest communities are poor, composed mainly of shade-tolerant species. Absence of grazing, expansion of woody plants, and high dust deposition from traffic have been the main reasons for the disappearance of several species. Key words: biodiversity, diabase, Lepraria bergensis, saxicolous communities, Silurian basalt.