yes twice, into the only part realy worth seeing is the grand canyon of Yellowstone. I know there's no way that someone going for the first time will pass up on seeing the geysers and hot springs. But there not worth the schlep especially with children. Exception being old faithful.
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I'd like to see anyone with a soul - kid or adult - not being in utter and complete awe of the Hayden Valley. Of the boiling water pouring into the Firehole River. Of the insane Minerva Terraces. Of Grand Prismatic Spring. Of the countless wildlife at each and every turn.
If something the Grand Canyon of the Yellowstone is one of the more boring places (relatively speaking, it's still not to be missed).