The Niasar cave (called Reis Cave by locals) is thoroughly man-made, except for one or two natural chambers near the entrance openings. The cave is believed to be a Mitra temple (Mitra was ancient Persian religion). Its first cut possibly dates back to the Partian (Arsacid) era, 248 BCE – 224 CE. Most Mitra temples like the Niasar cave have been built in full darkness. This cave has other entrance openings, some of which are located inside a rock which separates the upper parts of Niasar from the lower neighborhoods.
Fresh air Current circulates throughout the cave. In order to walk in most passages, corridors and even in small chambers of the cave, one has to creep and crawl. Even in some parts, the path is so narrow that it is not possible for one to pass through without stooping.
This cave has been dug out with the help of primitive implements and resembles a meandering stony tunnel in the breast of the Karkas Mountains. The same comprises of long and narrow passages, several chambers and wells. It is well worth mentioning that appropriate gear is required to gain access to this vicinity.
The Niyasar Cave is in three floors, and has a number of wells. Its ...see more passages and chambers cover approximately 500 square meters. The underground tunnels or passages are less than one square meter in area, and in some locations measure 100 x 70 sq. cm. Vertically 45 wells are connected to each other at an average depth of 118 m. This cave has four entrances and is of two separate sections. The central sector comprises of seven chambers in variable heights and very skillfully carved out.
The same is connected to the floor beneath by the wells and halls. The other portion is a lengthy passage with a gradual incline and is connected to other wells, this ends in a beautiful hall. At the extreme end of this sector there is a large area with several dug out chambers. The Niyasar Cave has 20 chambers, the largest of all being 28.6 sq. m. and the smallest 1.8 sq. m.