Answer:
the grand canal in Venice is 5 meters deep.
And, the Grand Canyon, in Arizona, USA, is more than 1 mile (0.6km) deep, in places.
There are canyons, in North America, that are actually much bigger and more spectacular than the American Grand Canyon:
in particular, there is one, in Mexico, called "Las Barrancas de Cobre". It makes the Grand Canyon look like a puddle of water in a pothole.