Ashdown Forest Wikipedia. Ashdown Forest is an ancient area of open heathland occupying the highest sandy ridgetop of the High Weald Area of Outstanding Natural Beauty.It is situated some 30 miles (48 km) south of London in the county of Sussex, England.Rising to an elevation of 732 feet (223 m) above sea level, its heights provide expansive vistas across the heavily wooded hills of the Weald ...