Yeouido Hangang River Park is probably the most iconic park in Seoul. It’s where all the television stations come to film their b-rolls for the 8 o’clock news. There’s a beautiful green area where you bring out picnic baskets and setup tents to relax in the grass. And even if you don’t have any picnic gear, you can order some fried chicken to wherever you’re sitting or just head over to the convenience store to get some noodles. Many Seoulites also bring their kids to the water park that’s in the center of the park to frolic in the summer heat. During the summer there are usually summer festivals where you can enjoy outdoor movies and concerts as well. Venture into some of the side streams of the Han River, and you can be in some isolated areas where you see the endangered red crane. You can also rent bikes at Yeouido Hangang River Park and take casual rides around the area. It’s a great outdoor space for some fun.
Also, there’s an ecological park more inland from the Han River. Check out the nature at Yeouido Park.