Researchers have shown that young children solve mapping tasks in small spaces, but have rarely tested children's performance in large, unfamiliar environments. In the current research, children (9–10 years; N = 40) explored an unfamiliar campus and marked flags' locations on a map. As hypothesized, better performance was predicted by higher spatial-test scores, greater spontaneous use of map–space coordinating strategies, and participant sex (favoring boys). Data supported some but not all hypotheses about the roles of specific spatial skills for mapping performance. Data patterns were similar on a computer mapping task that displayed environmental-scale videos of walks through a park. Patterns of children's mapping errors suggested both idiosyncratic and common mapping strategies that should be addressed in future research and educational interventions.