Could you share any impression on the rivers in Korea?

Thanks to the vicinity of the Han River from the embassy, I take promenade one or two hours every morning. Seeing the Han River, I used to be full of admiration. I had been to the Dong River (Donggang) in Yeongwol with my son. He likes rafting. Among the natural assets of Korea, I will choose mountains. Since our country has flat terrain, Korean mountains come into my mind most of all.