Within the Pungnap-dong Earthen Fortress in Seoul, various archaeological remains and artifacts that constitute an ancient capital have been excavated, including residential sites from the Proto-Three Kingdoms period to the Hanseong period of Baekje, as well as public buildings, ritual facilities, large-scale waste pits, pit dwellings, roads, waterways, and earthen fortess. The reconstruction focuses on Building Site No. 44 in the Gyeongdang zone and Pit-Dwelling Site No. Ga-30 in the Mirae Village area. Based on the traces of these structures, the study reconstructs various architectural elements, including floor plans, foundation construction methods, flooring treatments, pillar arrangements and frameworks, wall construction techniques and openings, as well as roof materials and forms. Building Site No. 44 in the Gyeongdang zone exhibits features characteristic of a transition to above-ground architecture, such as a rectangular floor plan, the construction of a separate foundation, a deliberately planned pillar layout, and independently built walls. Pit-Dwelling Site No. Ga-30 in the Mirae Village area, on the other hand, was designed as a pit structure with thick load-bearing walls to create a large interior space, differing from earlier forms. In this case, materials such as wood, stone, and earth were combined, reflecting an understanding of the distinct properties of each material. The significance of this study lies in the discovery that, although both buildings share similarities with pit dwellings in terms of floor plan and certain structural aspects, they also reveal attempts to implement new wall construction techniques in order to elevate the structures above ground and to construct large-scale buildings.