This paper aims to find new improvements from the post office building that mostly occupies the old building that is classified as a cultural heritage building. Architecturally, the conservation of cultural heritage has been written in regulations and laws, but the question is how to conserve the activity of the postal activities. Facing decreased customer transactions, increased competition from new technologies in digital, changing the city patterns, and the Post Office building as currently configured faces a challenging and uncertain future. Nearly half of the buildings that have been built since the 18th century are empty due to changes in the function of the post office, which no longer sends mail. The building of cultural heritage requires the conservation of content and containers that are adaptive to new functions. If conservation only relies on the uniqueness of buildings, it is found that there is a gap in the development of conservation models to adapt building and postal services to the digital influence and delivery of goods by the private sector and potential locations. By using the historical method of postal development, the history of the old city area, and the field survey to examine the shift of the present function, it is revealed that the conservation efforts that have been carried out by PT. The Indonesian Post Office not only focuses on buildings and activities but also attempts to increase the economic value of buildings in order to improve the image as post office service and strengthen the image as a gateway to the old city area of Semarang. It is found that the exposure activity was an old activity that was still attached to the post office building until now. Adaptive reuse is to accommodate activities that have relevance to post-service activities. As the architecture view, it is the unique architecture in the building and the city planning, because the post office building occupies a marker as the zero points of the city or also acts as a gateway to the old city at that time (it is possible to find other several cities). The post office building has a commercial value, which is quite high. Thereby adding commercial activities to get a better economic value can be increased (i.e., added activities for caffé, minimarket, coworking space). This recommendation will provide economic value for managers in dealing with the issue of a collapsed post office.