An Island of Wilderness in the City A visit to the Madrona Marsh Preserve is truly a unique experience. Come and explore one of the last remaining vernal wetlands in Southern California. The wetlands fill with rainwater in the winter and spring then slowly dry by late August. This natural wet-dry creates unique habitats and is the reason there is so much diversity of wildlife present. Note: The entrance gate to the Preserve is directly across the street from the Nature Center, where there’s plenty of parking available.