On Moab's fringe, the Colorado River emerges from a canyon, curves across the northern end of Spanish Valley and, instead of smacking into the high sandstone walls across the way, miraculously enters a second canyon - a portal.

Thanks to fault zones, geologic uplift, its own grinding nature and oodles of time, the Colorado only seems to be defying logic.The Portal Trail, a hiking and biking route, begins a short distance up this western canyon and, as it climbs, presents outstanding views of the river, the valley, Moab and the LaSal Mountains.

The trailhead begins at Jaycee Park, a seven-site campground on the right-hand side of scenic byway U-279, the road that parallels the Colorado to Potash and connects to the Shaffer Trail. The campground has a restroom but no hookups or water.

An informational sign at the trail's start notes that the path climbs roughly 1,000 feet to the Portal Overlook and warns that "hikers should anticipate careening mountain bikers, who may not have full control, due to the trail's steepness and looseness." The overlook is 1.5 miles from the trailhead, but, for the hardy and adventurous, the exposed trail continues another mile to Poison Springs Mesa.

At first the trail winds through sand and clinging oak and brush. This is not a good combination for two-wheelers, so bikers have found two or three locations where it is easier to connect with the route directly from the highway.

The trail chugs uphill, crossing terrain that includes ancient gravels from who knows where and slickrock en route to a point above the canyon's mouth. Hawks float the currents beside the sheer, black-varnished sandstone cliffs.

On a tilted shelf of rock, the Portal Overlook offers a perfect viewpoint to reconnoiter the valley and plateaus to the north and east. The city of Moab is laid out below, just across the Colorado River and Scott M. Matheson Wetland Preserve. The LaSals tower across the way, and to the north is Arches National Park. Distant windows and pinnacles are visible on the horizon.

If you go, remember that both hikers and bikers use the trail - and, though the trail is not a long one, be sure to take some water.