The El Capitan Trail is a 15 mile hike in Yosemite National Park that drops you off at the top of El Capitan, offering stunning views of Taft Point, Dewey Point, Half Dome, Clouds Rest, and North Dome. The hike is difficult but rewarding, offering views that can hardly be matched anywhere else. The trail is best used from May through October or early November, depending on snow levels.
Start on the Yosemite Falls trailhead and work your way up. Yosemite Falls can be anywhere from a huge flow to a slow trickle depending on the time of year. Hiking boots are absolutely necessary and hiking poles are a huge benefit. Say hello to rock climbers at the top as they finish their El Cap route.
Bring mosquito repellent in the summer. Bring lots of extra water and wear layers - even in the summer, weather in the Sierras is notorious for changing quickly. Be sure to watch your time - in October, start your descent no later than 2pm so you are in the valley by nightfall.
Additionally, while El Capitan has jaw-dropping views from the top, Eagle Peak is simply unbeatable. If you have the time, it's definitely worth the extra mile to summit. The trail changes from approximately ~14 miles to ~15 with the Eagle Peak summit.