When the first explorers reached the Grand Canyon and looked down at what is now the Colorado River, they thought it was a tiny stream. It wasn't until they reached the bottom that they realized it was a river 200 feet across, and they needed a boat.
It is difficult to understand the size of what you are looking at in the following pictures, but a few things can help. Look carefully at the trees around the mountains. They are not bushes or grass, but cedars and pines reaching heights of 80 feet. Look for people, houses, cars, anything that can be a reference. There are people at the top of almost every waterfall and around many rock formations.