By Luci Yamamoto

You need a couple of stout trees, a steel rope, and a devil-may-care vacationer. Ziplining—sliding between treetops while harnessed to a pulley on a cable—got its start in Costa Rica's rain forests, then spread northward.

A few spots, such as Oregon's Mount Hood Skibowl (skibowl.com), offer low-key summer zips. But the serious fun is in forests from Alaska to Hawaii. Screaming is encouraged.

▪ Juneau, Alaska Glide through old-growth conifers on seven zips and a suspension footbridge. (907) 321-0947, alaskazip.com.

▪ Ketchikan, Alaska Zipline and climb around an eco park.
(907) 225-8829, www.southeastexposure.com.

▪ Kapaa, Kauai, Hawaii Explore a majestic Norfolk pine canopy on six ziplines and two aerial bridges. Moonlight tours two or three times a month. (808) 482-1295, justlive.org.

▪ Park City, Utah The world's longest zipline has four cables, allowing a quartet of riders to race. Top speed: 45 mph. (800) 222-7275, parkcitymountain.com/summer/activities/ziprider.

▪ Park City, Utah This 1,500-foot zipline is the world's steepest and runs at rates up to 50 mph. (435) 658-4200, www.utah.com/parkcity/alpine_slide.htm.