Every city has its own landmark, which usually is a high-rise building with a visitor platform. From this rule, Seoul does not bail out for any exception and has built the Namsan Tower in the end of the 1960s.
It was built primarily as a TV and radio broadcasting tower, but has extended its purpose to a multifunctional building keeping a restaurant, a teddy bear museum, cafés.
Let’s get into the N Seoul Tower or also called Namsan Tower, as it is built on that mountain in the middle of Seoul. 
You cannot oversee the N Seoul Tower. It is Seoul‘s landmark just as the TV tower in Berlin, the Eiffel tower in Paris or the Liberty Statue in New York. It was built around 1970 as a broadcasting tower, but nowadays is used to attract a lot of visitors. The tower is 236.7m high. At night, the illumination of the tower changes hourly. You can get there by bus or either by cable car.
Inside the tower, you will find a café, a teddy bear museum, a restaurant on the top with a rotating deck and also a wine bar. 
On a clear day, you can see all over Seoul in a go-round 360 degress platform. The windows feature the directions and show you the distance to other capitals in the world. If you have to go to the toilet, even this job is worth getting it done on the tower.
At night, the view is really marvellous. 
Though the 63 building is the highest building in Seoul, the N seoul tower is more fun. Outside the towers on the observation platform you‘ll find a lot of love locks and inside tiles you can memorize your love with your darling. The tower itself is surrounded by a park, where you can relax under the trees. Sometimes performance are next to the tower entry. The park is said to be have been founded while Japan occupied Korea around 1897, who planted cherry blosom trees and paved streets up to Mt. Namsam (source: KTO). On the mountain itself, there are some Fortress Walls left and other cultural sites, so it makes sense to go there not only for a tower ride. You can also enjoy a cable car ride up there. Just take the green bus from Dongdaemun Station and ride up the hills where you can get off half the way. 