This geologic phenomenon is in a naturally protected region of the Czech Republic, just north of Brno. This is a giant series of underground limestone caverns and gorges that stretch for thousands of square kilometers. The region includes such highlights as the Macocha Abyss, a gorge 138 meter (453 foot) deep, which formed during a collapse of one of the underground cavern ceilings. In addition to caverns, Moravian Karst also contains well-marked bicycle trails and hiking paths to explore.