Abandoned military training ranges are important biodiversity refuges in the modern landscape. We surveyed 41 such areas across the Czech Republic in order to establish butterfly diversity and abundances. We found exceptionally high species richness, including many nationally-threatened rarities like Phengaris arion, Polyommatus dorylas and Zygaena punctum. We conclude that the high conservational value of these areas was maintained by the former army activities, which encouraged high habitat heterogeneity. and Pavel Vrba a kol.