The Sangseung Observation Post (상승OP) operates as a forward OP monitoring North Korean activities (currently Biryong Camp is in charge of the operation). Soldiers manning the post are on alert 24 hours a day. Visitors can view North Korean guard posts using binoculars, while iron fences and the vast Yeoncheon plain are also visible. Viewing the Demilitarized Zone (DMZ) that stretching across the plains offers a view of the habitat of a wide array of plants and animals that are rarely found elsewhere, such as eagles, goshawks, roe deer, and goats. Visitors can see the faces and movements of North Korean soldiers at their guard posts, and depending on the time, hear various North Korean propoganda broadcasts targeted towards South Korea. This is truly a front-line observation post on the DMZ. The No. 1 Tunnel (제1땅굴) is not open to the public since it is located in the Demilitarized Zone. However, a life-size model has been created and is on exhibit at the Sangseung OP, the closest observation post. The No. 1 Tunnel was discovered on November 15, 1974, by Sergeant Koo Hasa when his reconnaissance team sensed suspicious steam rising from the ground. After a few gunshots from a guard post in North Korea, Koo’s team started the investigation. It turned out that the tunnel was made by North Korean soldiers to infiltrate and aid in the invasion of the South.