Curt C.
Yelp
Old Faithful!
This nature trail is one of the coolest I've ever been on! I was sure to hike this at least once a day while I was in Yellowstone- each time there was something different going on.
The trail head is just behind Old Faithful. Part of the trail was donated by Michelin, which gives a good path to walk on. Then, it transitions into a boardwalk that takes you through the geyser basin, past bubbling steaming holes, hissing vents, colorful, deep pools of steaming hot water, and violently surging cones with geysers spraying out. If I didn't know better, I'd believe dragons were in here.
Watch out for buffalo! They were hanging out right next to the boardwalk one of the times I'd been.
You can access a side trail that'll take you to a good lookout spot that oversees Old Faithful and the structures around it.
I think the trail is about a mile and a half at the longest. Old Faithful isn't the only geyser around here- many are more powerful, but not as predictable.