The original entrance to the cave is on the eastern slope of a doline. The artificial entrance is placed on the edge of the doline bottom. Cave behind the entrance has a southern trend lying under the doline, a phenomena, that is not rare in our karst.
Železna jama consists of three chambers, interconnected with short galleries trough which the tourist trail with several bridges was made. In years 1962 and 1963, when the cave trail was under construction 8 m long artificial entrance was made on its western side, where natural gallery approaches the surface most. The original vertical entrance, chimney remained unchanged. Same, the eastern wall with the levels of the underground stream remained unchanged. Along the fault line there are several corrosion hollows and chimneys. On the western side because of the safety reasons few large fractured rocks were removed. Fractures of the rocks are parallel trough the slope of doline. There are also several grooves in the cave.
Characteristic form for the cave are curved stalactites, they are being bended during the growth by permanent air currents. The height of the first and second cave chamber is larger than their length and width. They developed from large shafts. Specially the first chamber are getting narrower downwards and under the cement trail forms about 1 m wide gallery only. The first cave chamber could be named after the numerous stalactites the Flowstone chamber. In the chamber there is below the ceiling stalagmite larger than 1 m. On the eastern side of the Flowstone chamber there are some fine cave draperies or flowstone curtains and a speleothem in a form that resembles and was in Postojnska jama cave named The cigar. The two chambers are connected by a meter long narrow passage with the signs of the water flow below its ceiling and above the passage floor. On the both sides of the chambers the water sinks because of the clay threshold in the bottom. The second chamber has a broader floor that was artificially levelled. The ceiling of the chamber is smooth, and on some places dissected with copulas. On some places on the west wall the aggressive percolating rain water hollowed out small cavities and flutes. Where the saturated water flows along the vertical walls eccentric speleothems grow. These are small hedgehog like needles (see fig. 10). There are numerous fractures and fissures cutting the walls if the two chambers along which because of inner tensions after the chamber was formed large stone blocks were separated subsided.

The whole cave was formed on the basins of the double shaft connected with a gallery. It was deepening and widening in the contact with sediments together with the lowering of the base level of the whole karst of Gorjuša. Towards those two shafts were all past and recent waters flowing that percolate trough the ceiling.
Although small there is variety of the forms in the cave. Evacuation forms are differently shape corrosion hollows, scallops, corrosion potholes, remnants of the phreatic cross sections of the galleries. Accumulation forms of speleothems are some stalagmites and stalactites, calcite flowers, calcite gours, small curtains and special stalagmite form cigar. There are also interesting fractures that developed because of the pressure release or pressure on the walls of larger hollows in the karst.