Mooney Falls is a stunning waterfall located on the Havasupai Reservation in the Grand Canyon. Visiting requires a $455 permit that are very difficult to obtain. To get permits you'll have to apply on February 1st at 8 am Arizona time on the official Havasupai Reservations website. Luck will need to be on your side because they usually sell out within a matter of minutes.
The hike to Mooney falls is 12 miles long, descends over 3,000ft and is extremely difficult. The permit is for 4 days and 3 nights and you will have to pack in and out all of your camping gear, food, and clothes. There is a water fill up at the campsite about 10 miles into the canyon from the rim. You can pay to take a helicopter for part of the journey for ~$100 each way but prices and availability can vary.
This trip requires a lot of planning so please do your research first but Mooney Falls is by far one of my favorite places in the entire world!