The big ditch! Stretching almost 280 miles in length, averaging a mile deep, and 10 miles wide, perhaps calling it the big ditch is a little understated.
The Grand Canyon is often visited by tourists on the rim. A study once concluded the majority of visitors spent less than 30 minutes actually seeing the canyon. To truly experience the canyon, you need to descend one of its side canyons, or hike one of the many trails that descends below the rim. It is an experience not to be missed. Plan on several days to really experience the place.
The north rim sees snow and cold temperatures in the winter, with the main access road being closed. It is a good place to visit in the spring, summer and fall. The south rim is accessible year around.
Summer is the most popular time to visit both rims, but hot. In the bottom of the canyon, temperatures can rise to 110+F. Hiking is still possible, but only for fit, experienced hikers carrying plenty of water. The scale of the canyon can be deceiving. What appears to be a short distance can be quite a ways, made longer by the heat.
It's hard to go wrong, all the hikes and canyons in the area are interesting. Just the sheer magnitude of the place makes an impact on you. Deer Creek, a short technical slot canyon on the north rim, offers what has to be one of the top 10 canyoneering experiences in the US. The canyon is exquisite, but the approach deters many.
Commercially guided river trips are also popular. Unfortunately getting a permit for private party river trips is generally a multi-year experience.