IN 2017, COLORADO’S capital city, Denver, joined a growing list of cities, including San Francisco, New York, Paris, and London, requiring green roofs on all new construction of more than 25,000 square feet (2300 m2). Green roof gardens already exist and have proven themselves. But rock gardens on roofs? Where there is a will, the materials, and the methods, there is a way. These two rooftop rock gardens in opposite hemispheres are proving that rocks, plants, and roofs can be compatible companions.