The ancient Polo city was built around the river Harnav, an ancient water body spoken of in the Puranas. It is believed to have been established in the 10th century by the Parihar kings of Idar, and was then conquered in the 15th century by the Rathod Rajputs of Marwar. The name is derived from pol, the Marwari word for “gate,” signifying its status as a gateway between Gujarat and Rajasthan. It was built between Kalaliyo in the east, the highest peak in the area, and Mamrehchi in the west, considered sacred by the local adivasis. Together they block sunlight for most of the day, which might provide an explanation for the otherwise mysterious abandonment of the ancient city. The 400 square km area of dry mixed deciduous forest is most lush between September and December after the monsoon rains when the rivers are full, but at any time of the year it provides a rich wildlife experience. There are more than 450 species of medicinal plants, around 275 of birds, 30 of mammals, and 32 of reptiles. There are bears, panthers, leopards, hyenas, water fowl, raptors, passerines, and flying squirrels (mostly heard, rarely seen), all living under a canopy of diverse plants and trees. During winter, all manner of migratory birds occupy the forest; during the rainy season there are wetland birds.