Ðulin ponor, Cave system in Ogulin, Croatia.

Ðulin ponor is the sinkhole where the Dobra river ends its course through a canyon in Ogulin. The cave mouth is a wide, low arch at the base of a light brown and grey rock face scored with vertical grooves and fractures, narrowing into a dark interior. Above the rock, a flat grassy ledge runs horizontally behind a low stone wall and a white fence, with a white-walled, dark-roofed building behind them.

The sinkhole is the end point of the Dobra, a sinking river that finishes its course through a canyon at Ogulin. Exploration of the cave system behind it has mapped 16,396 metres of passages. The name Đulin ponor comes from Đula, an older name for the Dobra in this area; old sources also call Ogulin "Đulin grad", and the city name may derive from the Latin ob gula, meaning throat or sinkhole.

The name Đulin ponor comes from Đula, an older name for the Dobra river here; older sources also call Ogulin "Đulin grad", and some link Ogulin to the Latin ob gula, "throat, sinkhole". A legend places Đula in 16th-century Ogulin: promised to an older nobleman, she loved the captain Milan Juraić, who died fighting the Turks, and she threw herself into the sinkhole. The tale rests on a crack in the cliff above the ponor shaped like a woman's profile, with nearby cracks forming a mustached man's face.

The sinkhole lies at the end of the Dobra canyon in Ogulin, where the river disappears into the rock below the cliff. The explored cave system behind the entrance runs 16,396 metres. The opening is visible from the town side, below the grassy ledge with its stone wall and white fence; the interior is not a walking route for visitors.

A crack in the cliff above the sinkhole is said to resemble a woman's face in profile, and locals link it to Đula; nearby cracks and bumps together form the face of a mustachioed man, the one for whom she supposedly jumped.