A 2,800-acre natural preserve dominated by the 800-acre Sheldon Lake. The Environmental Learning Center has one mile of wooded trails and more than 20 ponds for nature observation. Educational programs are on natural history, wetland habitats, pond ecology, fishing, alternative energy, composting and native plant gardening in the Texas Wildscape Demonstration Garden. Facilities are LEED certified utilizing a working wind turbine, photovoltaic panels, solar water heater, and geothermal system all accessible for public viewing. Admission is free; call for group reservations and fees for guided programs.