* Stay Here, Save the Earth

Billing itself as the first environmentally smart hotel in the continental U.S., the 193-room Sheraton Rittenhouse Square Hotel opened recently in Philadelphia. The hotel's atrium lobby contains a 40-foot-high forest of live bamboo trees, chosen because they take in carbon dioxide and produce oxygen at a 35 percent higher rate than any other plant. In guest rooms, night tables are made from recycled shipping pallets; bureaus are finished with a nontoxic lacquer process; and the walls are