The national park promotes public transportation but still allows cars to avoid deterring tourists, especially during the hottest and coldest months of the year.

BBC: Eco-scorecard to the world��s great attractions

With that comes opportunities of great interventions, new projects, rethinking urban transportation, creating vast new park systems, and experimenting with urban design strategies that might improve the quality of urban life.

BBC: Viewpoint: What makes an ideal city?

Grand Canyon National Park allows almost every kind of transportation into Grand Canyon Village.

BBC: Eco-scorecard to the world��s great attractions

That includes meals, housekeeping, linen service, transportation and activities, but it's twice the price of a standard Battery Park City rental.

WSJ: Senior Living It Up

Eco-friendly Philly boasts some 220 miles of bike lanes, good public transportation and the crown jewel of urban parks, 9, 200-acre Fairmount Park.

WSJ: Insider's Guide to Philadelphia |Journal Concierge

The city is celebrating the three-year mark by showcasing the event's centerpiece -- the under-construction Olympic Park -- and highlighting the progress made on everything from building work to transportation to getting sponsorship money.

CNN: London marks three years until Olympics

Visitor concessions like souvenir shops, lodging, transportation, equipment rental and food services will suffer from the decrease in tourism caused by the limitation in park hours.

CNN: STORY HIGHLIGHTS