Cheong Wa Dae, often called the Blue House in English, is the former presidential compound just north of Gyeongbokgung. Its blue-tiled roofs and mix of modern and traditional Korean architecture make it one of Seoul's most recognisable government sites.
Access rules can change, so check the current reservation system before planning a visit. It fits naturally with Gyeongbokgung, Bukchon Hanok Village, and the northern edge of central Seoul.