The Rocky filmmaker travelled to the eastern European republic last year (11) and used the Devetashka Cave, near Lovech, as the location for a scene in action movie The Expendables 2.
However, local officials have been penalised for allowing the Hollywood veteran to film at the site, as noise from the shoot risked disturbing thousands of the hibernating mammals.
Green campaigners took legal action, and this week (beg26Nov12) officials at the supreme administrative court in the country's capital Sofia imposed a fine of up to $6,630 (£4,143) after ruling that shooting a movie at the cave was "incompatible with the law on protected territories", according to AFP.
Devetashka Cave is among the most important bat habitats in Europe, and was home to 33,800 of the winged creatures before filming began. Their numbers slumped to just 8,500 after the movie crew had left, according to local experts.