So called because of its wilderness in the past, the Lost World is a forested karst plateau, bordered by the Bear´s Creek, the Dry Creek and the southern ridge of the Gardisoara Peak. In terms of hydrology two valleys appear here: the Bear´s Creek and the Dry Creek, the springs of which are very close and merge downstream, bounding an isolated plateau.
Lost World plateau hides a huge underground network of active galleries, betrayed on the surface by the existence of sinkholes masked by vegetation. Two of these are gateways for the underground area, through sinkholes with spectacular verticals, one of the largest karst Romanian heritage.
The Black Pit (with a 79 m vertical) is presented as a funnel with a diameter of about 50 m. The Gemanata Pit (with a vertical of 64 m) has above the entrance a natural bridge which divides it into two cavities (hence the name – the Twin Pit). The vertical of the pit is cut by a platform of logs and ice, formed at about -40 m, then another shaft is leading to the river which crosses the horizontal gallery, communicating with the network under the Black Pit. Another modest pit, the Cover Pit, is only 35 m vertically and does not communicate with the active streaming.