The altar is constructed using a base-to-top design meant to represent the harmony between the Earth (square) and Heaven (round).
Archaeological surveys suggest the foundation and some stone layers have been rebuilt and repaired repeatedly since the Goryeo Dynasty.
It is the official site where the flame for the National Sports Festival is ignited to symbolize the nation's origin.
The structure sits at an elevation of 469 meters above sea level.
During the Goryeo period, the altar was used specifically for rites performed by the King to pray for the prosperity of the country.
Chamseongdan Altar is a prehistoric stone structure located at the summit of Mani Mountain on Ganghwa Island, Incheon. Traditional accounts identify the site as the location where Dangun, the legendary founder of Gojoseon, performed sacrificial rites to Heaven. The altar consists of a rectangular lower level and a circular upper level constructed from natural stone without mortar. As of July 2026, access to the immediate vicinity of the altar is restricted for cultural heritage preservation, though the surrounding area remains a primary destination for hikers. The site serves as the starting point for the National Foundation Day torch-lighting ceremony each year. It is officially designated as Historic Site No. 136 of South Korea.
The viewing platform near the summit offering a wide-angle perspective of the altar against the backdrop of the coastline.
Wear sturdy hiking footwear as the ascent to the summit involves steep stone paths and wooden staircases.
Carry plenty of water and snacks, as there are no facilities once you begin the final steep climb toward the summit.
Check local weather reports specifically for Mani Mountain, as the summit is prone to high winds and rapidly changing conditions.
Do not attempt the hike in poor visibility or rainy weather due to the slippery nature of the steep rock paths.
The area around the altar may close periodically for conservation maintenance or extreme weather alerts.
Respect the physical barrier as the altar is a protected national monument; do not climb on the stone structures.
