The 35 miles of beaches and dunes which make up the county's 11 barrier islands provide habitat for coastal species, serve as critical storm protection for the inland communities, and form the basis of the area's thriving tourism industry. Elevation in the county ranges from mean sea level to its highest natural point of 110 feet (34 m) near the intersection of SR 580 and Countryside Blvd. in Clearwater. Due to its small size and high population, by the early 21st century Pinellas County has been mostly built out, with very little developable land left available. The county has maintained a fairly large system of parks and preserves that provide residents and visitors retreat from the city and a glimpse of the peninsula's original state.