Climb the hill along the city wall north of Dongdaemun Gate and look east. On the far side of the valley, you'll notice houses clustered around a crescent-shaped cliff. If you venture into the valley beyond it, you'll find more of these oddly curved, stark granite cliffs jutting out of the hillsides. These are not geological formations, but remnants of a time when the hills were used as quarries. The quarrying of granite first began during the reconstruction of Gyeongbok Palace in the 1860s and continued through the colonial period, when the stone was used in the construction of iconic buildings such as the Bank of Korea, Seoul Station and the former Government-General Building that stood on the present site of Gwanghwamun. While at least one known temple in the area features a cave-like grotto dug into a natural cliff face, another, Beopwang Temple, has a worship space inside a tunnel bored into the hillside, almost certainly built by the Japanese during World War II. Earlier this year, the film "The King's Warden," about the exile of the doomed teenage King Danjong, who was overthrown