The entrance is a vertical fissure in a hillside near the banks of the Kanger River, about 35 kilometers from Jagdalpur. Concrete steps and steel railings guide visitors down approximately 35 meters below the forest floor into a main tunnel roughly 200 meters long, though the cave's full network of lateral and downward passages extends much farther. It holds the distinction of being the longest cave on the Indian subcontinent. Inside, perpetual darkness and a remarkably stable climate prevail: annual mean air temperature hovers around 28 degrees Celsius with only slight variation, and the water in the cave's permanent and seasonal pools stays near 26 degrees. Five distinct chambers open through tall, narrow passages into a main hall where sound behaves strangely, amplifying whispers and swallowing shouts.

Kotumsar Cave lies within Dandakaranya, the legendary forest where the Ramayana tells us Rama, Sita, and Lakshmana spent a significant portion of their fourteen-year exile. For devotees, the cave is not merely geology but a living connection to that story. Flat rock surfaces inside the cave are interpreted as beds where the exiled royals slept. Raised platforms suggest places of worship. At the cave's deepest accessible point, the stalagmite Shivlinga draws pilgrims who believe Rama worshipped here daily. Local names for the cave reflect this layered identity: tribal communities also call it Gupanpal or Kutamsar, names that predate the Sanskritic overlay and suggest a much older relationship between these underground spaces and the people who live above them.

Kotumsar is India's most biologically explored cave, a distinction earned through decades of painstaking fieldwork. Dr. Shankar Tiwari conducted early exploratory visits in the 1950s, and in the 1980s, Jayant Biswas produced the first systematic map of the cave system during his doctoral research. The star of the cave's fauna is Indoreonectes evezardi, a blind, albino cavefish that navigates the permanent pools entirely through vibration and chemical sensing. Several cave-adapted arthropods have also been described from Kotumsar, including a cricket named Kempiola shankari in honor of Dr. Tiwari. Bats cling to the ceilings, spiders build webs in absolute darkness, and frogs inhabit the ditches between pools. In 2011, forest officials reported the discovery of a previously unknown chamber with distinctive interior formations, though difficult access has kept it closed to tourists.

Every year between mid-June and mid-October, the Kanger River swells with monsoon rains and the cave floods. Authorities close Kotumsar during this period, and before each tourist season, crews must clear accumulated debris from the entrance and passages. This seasonal rhythm shapes everything about the cave: the pools that sustain blind fish rise and fall, sediment redistributes through the chambers, and the delicate formations of stalactites and stalagmites, made of recrystallized calcium carbonate deposited over millions of years, continue their imperceptible growth. Oxygen thins as visitors venture deeper, and for safety reasons, entry beyond certain points is restricted. Parts of Kotumsar's network remain unexplored, with ongoing studies continuing to reveal new passages that may hold further geological or archaeological significance.

Kotumsar Cave sits within Kanger Valley National Park, accessible from Jagdalpur by road along NH 30 toward Sukma. The nearest airport is Maa Danteshwari Airport in Jagdalpur, and the city is also connected by rail. From the park's main entrance at the Kotamsar barrier, the cave lies a few kilometers into the forest. The site at approximately 560 meters above sea level offers no hint of the labyrinth below until visitors reach the fissure in the hillside and begin their descent. It is a place where the surface world simply ends, and something older, darker, and far stranger begins.