Mars may or may not have water, but it does have a gigantic, beautiful canyon that puts America’s Grand Canyon to shame. It’s 2,485 miles long, to the Grand Canyon’s 277 river miles, and 124 miles wide, to the Grand Canyon’s average 10.
The Grand Canyon could fall into this canyon and not make a sound. The Mars canyon probably has minor branches that are bigger and longer than the Grand Canyon.
Plus, the Mars canyon has a really sci-fi sounding creation story. According to the European Space Agency:
As the Tharsis bulge swelled with magma during the planet’s first billion years, the surrounding crust was stretched, ripping apart and eventually collapsing into the gigantic troughs of Valles Marineris.
Also, no tourists. Yet.
The Solar System's grandest canyon, PhysOrg.