Foiba (plural: foibas or foibe)'s a type of deep natural sinkhole, doline, sink and's a collapsed portion of bedrock above a void. Sinks may be a sheer vertical opening into a cave, or a shallow depression of many acres which are common in the Kras (Carso) region, a karstic plateau region shared by Italy, Slovenia and Croatia. In karst areas, a doline, sink or sinkhole's a closed depression draining underground. It can be cylindrical, conical, bowl-shaped or dish-shaped. The diameter ranges fr… (More on Foibe)