Pu'u Oo Volcano Trail is a 5 mile out and back trail located near Hilo, HI that offers scenic views. The trail is rated as moderate and primarily used for hiking.
Fascinating hike over a lava trail with a couple of short sections through forests. However, I would not call it easy since there are several steep slopes with loose gravel and one needs good boots and decent balance in other sections. The trail is of interest to bird watchers and those curious about volcano ecology. For a shorter hike just go in two miles or so and there is good variety. Great views of the observatories on Mauna Kea.