Representing human spatial knowledge has long been a challenging research area. The objective of this paper is to model a route description of human navigation where verbal descriptions constitute the inputs of the modeling approach. We introduce a structural and logical model that applies graph principles to the representation of verbal route descriptions. The main assumption of this approach is that a route can be modeled as a path made of locations and actions, both being labeled by landmarks and spatial entities. This assumption is supported by previous studies and an experimentation made in natural environment that confirm the role of actions, landmarks and spatial entities in route descriptions. The modeling approach derives a logical and formal representation of a route description that facilitates the comprehension and analysis of its structural properties. It is supported by a graphic language, and illustrated by a preliminary prototype implementation applied to natural environments.