Tucked all the way back in Manoa Valley, this is a gem of an arboretum operated by the University of Hawaii. Hike to a waterfall or sit and enjoy beautiful views of the valley. You'll also see an ethnobotanical garden and one of the largest palm collections anywhere—all within a park-like setting. Its educational mission means there are regular talks and walks with university faculty. Docents give 60- to 90-minute tours weekdays at 10 am. There are also self-guided audio tours. www.hawaii.edu/lyonarboretum. COST: $5 donation. OPEN: Mon.--Fri. 8--4; Sat. 9--3.