The Pine Creek Loop in Tonto Natural Bridge SP takes you to the largest natural travertine bridge in the world and a 400 foot long tunnel with beautiful turquoise pools in the bottom that opens to a gorgeous riparian area.
There is a fee to enter this area $7 per adult as of 2025 (see AZStateParks.com for updates). There are 4 trails with many viewpoints from the parking lot, all of which are out and back. We followed the recommendation of the ranger working at the visitor's center and took the Gowan Trail down to the observation deck located in the creek bottom. This park can be very crowded on weekends and holidays. We went on a day that was a little bit rainy and had the place to ourselves.
The trail to the observation deck was steep in spots but very well maintained. From the end of the observation deck you can explore underneath the bridge which is full of deep turquoise pools. The travertine dissolved in the water is what causes it to have the turquoise color. There are some arrows painted to mark the best way to get through the 400 foot long tunnel. When you come out the other side you're in a beautiful riparian area. If you're lucky you might see some coatimundi while exploring here. You can then take the Anna Mae Trail for a short distance and then take the Pine Creek Trail back up out of the creek.