Indoor navigation is very useful in reality. An indoor navigation system requires an appropriate indoor model that represents the indoor space entities as well as topology and supports indoor distance computation. Indoor distance computation differs significantly from its outdoor counterpart, due to the indoor space characteristics. On the other hand, information about an indoor space is described in digital building information (DBI) formats like the Industry Foundation Classes (IFC). In such formats, geometric representation of entities is the focus but the topology is only implicit or even incomplete. Thus, constructing indoor navigation systems faces two major technical challenges: 1) indoor distance computation; 2) indoor space model creation from raw DBI. This paper presents a prototype system that addresses these two challenges. The system provides functions to process raw DBI files, employs PostgreSQL with PostGIS to manage the information carefully extracted from those files, and offers indoor navigation service that supports indoor distance computation. The system also presents an app that accesses the indoor navigation service from mobile terminals.