The outdoors can offer children a rich space for learning and inspires authentic mathematical opportunities. The author describes the experiences her kindergarten students have when when they spend many hours each day, exploring their vast play yard and engaging in play-based activities typically done inside a classroom. She also chronicles the Beautiful Tree Project which became a highlight in their mathematical journey, helping to articulate the vision for the necessity of outdoor play and the rich possibilities of child-centered math explorations. Some of the activities that were part of the project included observation, classification, and measuring. It also inspired art, storytelling and community action from the students.