Jamsil Hangang Park
is a great place to see the sunset and night view in Seoul.
You can see the night view of Lotte Tower and Namsan Tower, and the green lights of Jamsil Bridge
create a gorgeous night view. On a clear day, you can see the sunset behind Namsan, and it is a Hangang Park with easy access because it is close to Jamsil Saenae Station.