Holy Land

The planet was a lovely, unspoiled Earth-like world; what Earth might have been like if men had treated her with compassion instead of lust. Virgin forests, white beaches, pristine deserts. The few dozen cities there either blended perfectly with the environment (one was totally underground) or were brazen statements of human ingenuity: Oceanus, in a coral reef with six fathoms of water over its transparent roof; Boreas, perched on a sheared-off mountaintop in the polar wasteland; and the fabulous Skye, a huge resort city that floated from continent to continent on the trade winds. We landed, at the jungle city, Threshold. Low buildings of native stone and wood rested among ten-meter-thick tree trunks. They were connected by unobtrusive stone paths, with one wide promenade meandering off to the beach. Sunlight filtered down in patches, and the air held a mixture of forest sweetness and salt tang.
-The Forever War, by Joe Haldeman