Han-gang River Cruise ★★
The Han-Gang River, crossing over the heart of Seoul, has many scenic attractions and pleasures along its bank. The Han-Gang river cruise is a must for foreign visitors to Seoul. The cruiser is about 1 hour long.
Open : daily 11:30-22:00
Admission fee : adult 6,800 won/ children 3,400 won
Information: (02)785-4411 (in Korean)
How to go : exit #3, Youinaru station(527) on Purple #5 line 

Seoul Tower 
It is located on top of Mt. Namsan in the center of Seoul. In the Seoul Tower, people can enjoy a beautiful panoramic view of Seoul city while having a drink or a meal at the nice revolving skyline restaurants of the 5th floor. It has decks on the 2nd and 3rd floors and aquarium, marine life museum, and video games on the 1st floor at the main building. The height of the Seoul Tower combined with the height of Mt.Namsan is 480m above sea level.
Open : daily 09:30-23:00
Admission fee : adult 7,000 won/ children 5,000 won
Information: (02)772-1660 (in Korean)
How to go: about 2km South from City Hall
takes about 10 minutes by taxi at Myeongdong station(24) on Blue #4 line