Indoor routing represents an essential feature required by applications and systems that provide spatial information about complex sites, buildings and infrastructures such as in the case of visitor guidance for trade fairs and customer navigation at airports or train stations. Apart from up-todate, precise 3D spatial models these systems and applications need user interfaces as core system components that allow users to efficiently express navigation goals and to effectively visualize routing information. For interoperable and flexible indoor routing systems, common specifications and standards for indoor structures, objects, and relationships are needed as well as for metadata such as data quality and certainty. In this paper, we introduce a classification of indoor objects and structures taking into account geometry, semantics, and appearance, and propose a level-of-detail model for them that supports the generation of effective indoor route visualization.