Kokohead Crater Botanical Gardens

The Kokohead Crater Botanical Gardens are inside the old volcano Kokohead.  There is a trail here that you can go all the way around as a easier hiking trail, or just go a little ways and see all the best stuff if you're wearing sandals or something like that.  I'd suggest taking a right at the fork after the plumeria grove and then continuing until you find the large cactus area if you want the shortened version.  There are lots of beautiful plants here, but just a word of warning, this botanical garden is not very well maintained and everything isn't always in bloom.  But if you want a nice walk through nature, or to say you've been inside a volcano, you can have a nice experience here.

Dole Plantation

The Dole Plantation is a fun place to stop if you're heading through the middle of the island.  They have activities you can pay for here, such as a corn maze and train tour, but even if you don't want to do those things, stop by to see how a pineapple looks when it's growing and to try the delicious Dole pineapple ice cream.