Closed depression in karst which is in size between sinkholes and poljes. Uvalas with a flat, sediment-covered bottom are also called Karstwanne (lit. karst trough).
The name uvala is common language in parts of former Yugoslavia, Croatia, Bosnia and Herzegovina, Montenegro and Serbia. It refers to closed karst depressions, significantly larger than sinkholes, usually elongated or irregularly shaped with irregular bottoms. As this type of karst depression is widespread, uvala has become the technical term used internationally. It is, so to speak, the intermediate stage between the smaller sinkholes and the larger poljes. However, the discrimination between the terms is mostly empirical and poorly supported, so that differing opinions regularly arise. For this reason, the technical term is reluctantly and little used, and it is even recommended that the term be abandoned altogether.
The essential characteristic of an uvala is a depression, closed on all sides with an irregular outline and several centres of depth. Like dolines and poljes, it is drained underground by ponors. Uvalas can be formed by the coalescence of several sinkholes as a result of progressive karstification.