Distance: 2 miles (3.2 km) round trip
Trailhead Elevation: 4,000 feet (1,200 meters)
Total Elevation Gain: 300 feet (90 meters)
The Squiggly Lines Explained: If the Vernal Fall footbridge is your final destination, the red line, which ends at the bridge, is the only one you care about. If the sight of Vernal Fall lures you past the bridge, you'll be following the yellow line, which leads to the top of the fall. The purple line continues from there to the top of Nevada Fall. The crowd thins out noticeably on this section, though it's still one of Yosemite's most popular trails. The green lines mark alternate routes along the John Muir trail, which is longer and less scenic, but not as steep as the routes beside the waterfalls.
The trail is level until you round the bend at Sierra Point. From there on it climbs more or less steadily all the way to the top of Nevada Fall. Even if you just go to the footbridge, you'll notice the incline. Though this trail seems to be a magnet for people in flip flops and even high heels, sneakers or hiking boots will serve you better, particularly if you elect to continue past the footbridge along the steep, rocky, and slippery ascent up the steps beside Vernal Fall.
The free shuttle buses can drop you off right at the trailhead (where the green hikers are), but it's also a flat, easy walk to the trailhead from the nearest parking lots, the Curry Village lot and the Trailhead Lot. Zoom out a notch to see them.