I took the picture below when we flew back from Hilo, Big Island via Kailua-Kona to Honolulu. It shows the two great and mostly dormant volcanoes of Big Island. Mauna Loa (in the background) is a destination for tough hikers. You need a four-wheel drive to get to the trailhead and a hiking permit to go to the summit. Mauna Loa means "long mountain", and it is a long way the summit.
Mauna Kea (in the foreground) has a collection of the most advanced telescopes on earth on its top. The "seeing", as astronomers call the atmospheric conditons, is excellent, and Mauna Kea is perhaps the best place for a telescope on our planet.
A page with Relief Images shows the different volcanoes on Big Island.
If you are interested in astronomy, here are a few links to the telescopes on Mauna Kea:
Keck Observatory - Mauna Kea, Hawaii.
The Gemini 8m Telescopes Project - The Gemini Project is an international partnership to build two 8-meter telescopes, one on Mauna Kea, Hawaii, and one on Cerro Pachon, Chile. The telescopes and auxiliary instrumentation will be international facilities open to the scientific communities of the member countries.
NASA Infrared Telescope Facility Home Page - The IRTF is a 3.0 meter telescope optimized for infrared observations, and located on the summit of Mauna Kea, Hawaii. The observatory belongs to NASA and is managed and operated for NASA by the University of Hawaii Institute for Astronomy.
Canada-France-Hawaii Telescope - CFHT is a joint facility of the National Research Council of Canada, the Centre National de la Recherche Scientifique of France, and the University of Hawaii. The observatory is located atop the summit of Mauna Kea, a 4200 meter, dormant volcano located on the island of Hawaii.