They can also be dangerous. Our desire to get up close can put us in danger of getting too close and losing our footing. Once while hiking near Steamboat Springs, CO, to see a waterfall up close, my husband heard our friend's feet scrambling in the gravel to stay on the trail. My husband was close enough that he grabbed the friend and prevented him from falling in the crevice.
I believe the grandest waterfalls are in Yosemite CA. The park is awe inspiring. I suggest you go in the winter, when there will be fewer people.