Landmarks are basic ingredients in route descriptions. They often mark choice points: locations where travellers choose from different options how to continue the route. This study focuses on one of the loose ends in the taxonomy of landmarks. In a memory-based production experiment in which respondents described routes they had seen on a map, we studied the distribution of two types of landmarks at choice points: route-external and route-internal descriptions (‘take left “at the barber shop” or “at the second intersection”’). We systematically varied route length and the degree of visual clutter in the map. Cluttered maps resulted in a higher proportion of external landmarks, which we explain in terms of their higher degree of referential robustness. Internal landmarks were preferred as routes were longer and thus required more memory load, suggesting that they are more basic or ‘skeletal’ in route descriptions. Copyright © 2013 John Wiley & Sons, Ltd.