This paper describes the design and evaluation of Uncover: a mobile application that supports users in exploratory pedestrian behavior to gain situational awareness of their immediate environment. The design was based on guidelines derived from foraging theory and relies on egocentric views, which keep the virtual content automatically aligned with the real world. We carried out two studies with Uncover, which examine the successfulness of design choices aiming to support tourists' city exploration while interfering with experiencing the surroundings as little as possible. A lab study tested the effect of different marker and background types on the time to recognize the direction with most content. The designs performing best were implemented in the final prototype, and a field study analyzed the exploration behavior tourists and visitors exhibited while using it. The study showed that supporting the exploration can be improved by enabling features that are either disabled by default or not available at all in commercial map applications, like egocentric orientation of the map, providing images of venues just by pointing to their direction, and displaying clusters of several venue types.