Wowzer a not to miss! I have been to many national parks and nature preserves and this has to be up there in the top ten! A beautiful self-guided walk through the geothermal valley, surrounded by hotsprings, very cool vegetation and birds and all at your own pace, we took about three hours, you could do it in less or take the better part of the day. Absolutely stunning views and lots of birds to watch. We also took the boat trip at the end it was great and a better chance to see more geysers. Plus added benefit the Cap'n was great and had spent time piloting in Alaska waters so we had a good chat about that too. The walk is also easy for kids and even better when you are done there are buses that bring you back to the top/carpark so even good for us older folks and people with kids. :)