After our visit to Montezuma's Castle, my brother and I opted to go check out Montezuma's Well. Montezuma's Well is free to access and is located about 4 miles from the castle. Basically you take one more exit north along the I-17 from Montezuma's Castle and follow the signs from there. It wasn't hard to find at all.
The park is paved and has two stops. The first stop is a small area where you can check out the remains of the floor plan of a hut. There are still some holes in the ground where the wooden structures that solidified the house were located. Worth a few minute stop to check out:
After leaving the hut's foundation you drive a bit more before you come to a somewhat larger parking lot. At this point, you'll also come to a ranger station where you can learn about the well and the surrounding area from the volunteers there. Again, there is no charge to visit here.
A short and manageable uphill hike takes you to the well. It sort of sneaks up on you and just as you crest it, your jaw will drop as you take in the depth and breadth of the area. There is also an Native American dwelling on the side of the cliffs.
There is a lot of information here and it is pretty amazing that the water you see in the pool below is over 10,000 years old. Also, anything put into the depths of the pool is summarily pushed up (something that even the natives knew about).
You can tour the well and I think you can walk down to the base, but when we visited, the access to the base was closed off. The trail then continues to the creek below where some of the water from pool dumps out below.
All told, we spent about 30 minutes here. There isn't any shade here (except near the creek). So plan accordingly for the weather. There are bathrooms however.