A decent overview of the Cheonggyecheon River Restoration project from Spacing Toronto will help to see all the phases from the demolition of the expressway to the finishing of the promenade that has become the heart of Seoul's social life.
Images from the Rights of Way blog show the remnants of the original elevated expressway that orginal covered the river. Ironically, the mayor who originally spearheaded the elevated highway was the very same who pushed for the rehabilitation and restoration of the Cheonggyecheon River. So, in the end, it's a good thing that some politicians, in their search for approval, end up backing projects that actually improve quality of life.