Hiking through the lava flows at Hawai'i Vocanoes National Park, it's hard to know which way to go. There's no trail per se, just hard rock, and very few natural landmarks to oriente you. In response, the Parks Department built large piles of lava rock, i.e. cairns, every hundred meters or so. You walk from one pile of rock to the next as you move through this incredible landscape. I love it, because you never have to really pay attention to where you are going. Just enjoy the scenery. [NOTE: See Habitats in Hawai'i and Amy, Luke, and the Lava Flow for more on this wonderful trip].