Zayandeh-Rood, 270 km long, is considered to be the most significant river of Isfahan province. Furthermore, this river plays an effective role on the climatic conditions and the humidity of the region, and provides excellent opportunities for recreation. Several historic bridges have been constructed over it. Zayandeh-Rood passes through the city of Isfahan and pours into the Gavkhooni swamp. Because this region is situated on the borders of a large desert, Gavkhooni swamp enjoys particular significance as regards its influence in the climate of the region, absorption of migrating birds, and providing excellent habitat for different types of aquatic creatures. Migrating birds come to this swamp from the north in the cold season, and the south is the warm season. Niyasar Cave: This cave, situated 30 km northwest of Kashan, is considered to be one of the most remarkable caves made by the human being. This cave was dug in Karkas Mountains about 2000 year ago, and has several halls, wells and rooms. The entrance of this wonderful labyrinthine cave is 3.5 m high and 2.5 m wide. The other major caves of this province are Ghahreman cave, 12 km west of Isfahan, Shah-Ghandab Cave in Shah-Reza and Shah-Shokr Cave on Shah-Reza-Samirom road. Verton Springs: This is a collection of mineral water springs which lie 43 km from the lsfahan-Yazd road. This region possesses several baths which have been built to use for curing rheumatism.