Karst formations

thumb|Livanjsko Polje in Bosnia is the largest polje in the world (Mount [[Dinara visible in the background).]] A polje, also called karst polje or karst field, is a large flat plain found in karstic geological regions of the world, with areas usually in the range of 5–400 km2 (2–154 sq mi). The name derives from the Slavic languages, where polje literally means 'field', whereas in English polje specifically refers to a karst plain or karst field.

thumb|upright=1.4|Cave labeled with the six most common types of speleothems: flowstone, columns, drapery, [[stalagmites, stalactites and straws]] A speleothem (; ) is a geological formation made by mineral deposits that accumulate over time in natural caves. They can take a variety of forms, depending on their depositional history and environment. Common forms include stalagmites, stalactites, and flowstones.

thumb|The river Dobra (Kupa)|Dobra enters a 17 km long cave system at in [[Ogulin, Croatia.|276x276px]] A ponor is a natural opening where surface water enters into underground passages; they may be found in karst landscapes where the geology and the geomorphology is typically dominated by porous limestone rock. Ponors can drain stream or lake water continuously or can at times work as springs, similar to estavelles. Morphologically, ponors come in forms of large pits and caves, large fissures and caverns, networks of smaller cracks, and sedimentary, alluvial drains.

Suffosion is one of the two geological processes by which subsidence sinkholes or dolines are formed, the other being due to collapse of an underlying cave or void, with most sinkholes formed by the suffosion process. Suffosion sinkholes are normally associated with karst topography although they may form in other types of rock including chalk, gypsum and basalt. In the karst of the UK's Yorkshire Dales, numerous surface depressions known locally as "shakeholes" are the result of glacial till washing into fissures in the underlying limestone.

cave with significant vertical passages

lake mainly located beneath the Earth's surface

local toponym in some regions in Croatia, Bosnia and Herzegovina, Montenegro and Serbia for a closed karst depression

lake

thumb|Grotta Plutone is a foiba close to Basovizza, Trieste ([[Italy)]]

lake formed as a result of the collapse of subterranean caves, especially in water-soluble rocks such as limestone, gypsum and dolomite

limestone stack in Poland

waterfall inside cavern

geological reserve in the Autonomous Republic of Crimea, Ukraine