The Trebišnjica River is one of the longest underground rivers in the world, located in Bosnia and Herzegovina. It flows primarily through the Herzegovina region and is known for its clear blue waters. The river originates from the Popovo Polje karst field and travels approximately 100 kilometers before emptying into the Adriatic Sea. The Trebišnjica is significant for its ecological and hydrological features. It supports diverse wildlife and is a vital water source for the surrounding areas. The river also plays a crucial role in local agriculture and hydroelectric power generation, contributing to the economy of the region.