Really lovely trail all along the way. Easy to follow except at the stream crossings. There are no bridges so if the water is up like it was for us you will need to wade. I built a rocky causeway to pass the first crossing upstream but the downstream crossing was much too deep and we had to get our feet wet. The spring is not visible from the trail and appears on the map to source several miles away which may be visible from another road which passes through that way(just by visual inspection on a map). The trail was easy to follow in most places though some spots we lost it due to sharp turns and lack of arrows indicating the proper path which caused us to do some unnecessary ledge crawling. The sentry bluff trail(Blue diamonds) travels along with part of the Natural bridge trail(Yellow Diamonds) close to the parking area where the natural bridge can be seen across the creek. However unless coming in a dry/low water season you will be getting your feet wet to see the natural bridge or to hike any trails on the other side of the stream. Both the entire length of the sentry trail we took and the finale of the natural bridge at the end were stunningly beautiful. A spraying water fall into the keyhole of the natural bridge gave rise to a small rainbow next to a a large snaking tree which climbed the height of the bridge into the canopy above.
Definitely well worth the visit. Better trail marking in places and bridges for stream crossings would make my 5 star review.