It means "Unification Observatory".
Built by an army unit in 1983,Goseong Unification Observatory (700m) was the closest place from where you could view the Mt. Geumgangsan before it was opened to South Koreans. The closest part of Mt. Geumgangsan is 16km away and the farthest part is about 25km away. From the Observatory, you can see Haegeumgang, and the islands nearby, Manmulsang, and Hyeonjongam. On clear days, you can also glimpse various peaks of Mt. Geumgangsan such as Ilchulbong (1,552m), Chaehabong, Jipseonbong, Yukseonbong, Gwaneumbong, and even the greatest peak of Mt. Geumgangsan, the Birobong Peak. Goseong Unification Observatory is the closest location to the north, and many people who visit are those who had to leave their home and were separated from their families during the Korean War. You can see monuments built in the hope of reunification here.