I read a lot of reviews before venturing to Waimea, and I'm glad I ignored the negative ones and came anyway.
Yes, the $15 pricetag is a little steep, but not too much. This is a sprawling, wonderful arboretum/botanical garden. That's really what it is, and thus what you should be expecting. Expect a natural garden with a huge diversity of tropical plants from around the world -- with a little waterfall and some ancient Hawaiian villages / cultural sites thrown in, as well.
Everybody seems to focus on the waterfall, and many people we saw ignored everything else and went straight to the water hole for swimming with the falls. They are fairly unimpressive, not nearly as beautiful as others I have seen, and overcrowded with swimmers. So if you are going just for that, prepare to be let down.
Good thing we didn't go for that. I liked seeing the archaeological sites, though I wish there were more informational signs up around the different locations and reconstructed buildings. I also would have appreciated some information on how to play the games at the traditional Hawaiian games location (it seemed interesting, but there was nobody there and nothing posted to say how to play them -- and no cell signal to look the rules up online)
Having said all that, we meandered for hours -- yes, hours -- amongst the sprawling paths, and visited nearly every location (grouped by plant type and geographic place of origin), and found it fascinating, relaxing, and enjoyable. We only made it to the waterfall after 2-3 hours of exploration, and it was just as lackluster and tourist-riddenas we had anticipated, so we simply turned around and came back.
All in all, it was worth it, although I agree the price could maybe be more reasonable at 1/2 to 2/3 of what it currently is.
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