Mt. Ohdu Unification Observatory, Military observatory in Paju, South Korea.

The Mt. Ohdu Unification Observatory is a four-storey building (three above ground plus a basement) on the 118 m Odusan fortress site where the Han and Imjin rivers meet. Its glass-walled observation rooms on the third and fourth floors face north over the river to North Korean territory, including propaganda villages, and the circular hall looks toward Songaksan in Kaesong.

The observatory opened on 8 September 1992, after the Blue House ordered a review of the Odusan development on 22 January 1990 and construction began with a groundbreaking ceremony on 4 June 1991. By August 2010 it had received more than 16 million visitors. It stands on the site of Odusan Fortress, an old earthen fortification at the Han and Imjin confluence.

The facility displays photographs and maps that document the division of the Korean peninsula. Visitors can explore different rooms that show how this separation has shaped both sides.

Take city bus 033 from Geumchon Station on the Gyeongui-Jungang Line; the ride takes about 30 minutes to the Tongil Dong-san public parking lot, from which the observatory is a 20-minute walk. The shuttle bus that once linked the parking lot and the observatory was discontinued when admission became free in 2024. Entry is free, but the site can close temporarily when military access restrictions apply.

From the roof, you can see a stark contrast between South Korean urban development and the more rural landscape across the river. This difference illustrates how the two sides have developed in opposite directions.