When we talk about the wonders of our Bulgarian nature, we must not overlook the karst formations. My colleague, English teacher - Reni Valkova, along with his students explore the karst field near the town of Zemen, made ​​a film about him and participated in a competition of UNESCO. The film was awarded first prize in the category for 2012. The interest of students and continues today. Reni Valkova hosted an open lesson in English based on topic  karst  . In the lesson is used ENVISION - system that is innovative Bulgarian educational product.