The Fortress of Ponor represents without doubt the greatest karst phenomena in Romania, known and appreciated all over the world.

The Fortress of Ponor are made up of three large stone circles, situated in a huge 300 m deep forested depression, its upper diameter surpassing 1 km. The surrounding slopes that encircle the depression are cut only in a single spot, by the Cetăţi valley canyon.
The access trail departs from the forestry road and gradually descends through the forest on rugged terrain, parallel to the Cetăţi valley, until it reaches the so-called Doline I.

The 150 m lateral stone wall in the West is perforated by an over 70 m cave portal, in which the Cetăţi valley flows.

The giant portal of the Fortress of Ponor suggests a gothical ogive that became a sort of symbol for the Apuseni Mountains karst. The spruce trees that are hanging in the stone walls are the only comparison term for the great size of the portal and of the wall into which it is carved. To the left, the upper part of an even higher stone wall is seen, surrounding Doline III, with the two wooden balconies hanging over the precipice.

In the right side of the portal, a spit of scree ascends through under an arcade into Doline II. This is actually a 200 m deep circular pothole, having two windows at its base: one represents the access to the Doline I under the portal, while the other opens to the underground tunnel of the cave system.

Also under the portal, to the left, the flooded tunnel brings to the light only for a short while the waters originating in the Lost World plateau which flow underground in Căput cave.

Doline III is reachable through Doline I, after climbing the metal stairs from the left side of the portal and surpassing the stone edge that separates the two dolines. Doline III has a triangle shape with a 300 m long margin, in the middle of which scree slopes descend towards another cave portal. To its left side, above the access gallery into the subterranean sector, there is a vertical stone wall over 200 m high, with small vegetated edges. In the Southern part, the tourist trail climbs on the steep slope of a torrential valley towards the balconies.