You'll comprehend space in new ways atop the appropriately named Island in the Sky. This 6000ft-high flat-topped mesa drops precipitously on all sides, providing some of the longest, most enthralling vistas of any park in southern Utah. The 11,500ft Henry Mountains bookend panoramic views in the west, and the 12,700ft La Sal Mountains are to the east. Here you can stand beneath a sparkling blue sky and watch thunderheads inundating far-off regions while you contemplate applying more sunscreen.
The island sits atop a sandstone bench called the White Rim, which indeed forms a white border 1200ft below the red mesa top and over 1500ft above the river canyon bottom. An impressive 4WD road descends from the overlook level.
The complimentary video at the visitor center provides great insight into the nature of the park. Remember to keep your park entry receipt – admission to Island in the Sky includes entry to the Needles, too.
Overlooks and trails line each road. Most trails at least partially follow cairns over slickrock. Bring lots of water and watch for cliff edges!