Royal Oak Foundation

By joining the Royal Oak Foundation (New York, NY; 800/913-6565, ext. 205, or 212/480-2889, www.royal-oak.org), American visitors to Britain can enjoy unlimited free entry to more than 350 National Trust destinations: historic houses, gardens, castles, nature reserves and UNESCO World Heritage Sites.

At hotels and holiday cottages owned by the National Trust, Royal Oak members also get a 25% discount on all published room-and-breakfast rates and a 10% discount on all published seasonal breaks, plus a free room upgrade.

Foundation membership costs $55 annually ($90 family), tax-deductible. The foundation is the US partner of the nonprofit National Trust of England, Wales & Northern Ireland.