Ponors are found worldwide, but only in karst regions. The entire Adriatic watershed within Bosnia and Herzegovina sits on Dinaric karst, with numerous explored and probably many more unexplored ponors and underground flows. There are also several places in southeast Europe (Bulgaria, Croatia, Czech Republic, Hungary, Romania, Montenegro, Slovenia) with the name Ponor due to associated karst openings. There are significant geological ponors in the Carpathian Mountains, the Dinaric Alps, Greece, Turkey, and parts of the southern United States.