Hawaii Route 21, also known as the Hawaii Belt Road, is a scenic highway located on the island of Hawaii, also referred to as the Big Island. This route connects various towns and attractions, providing access to beautiful landscapes, including lush rainforests and stunning coastlines. The highway stretches approximately 50 miles, linking the towns of Hilo and Kailua-Kona. Travelers can enjoy views of Mauna Kea and Mauna Loa, two of the island's prominent volcanoes, while also passing through diverse ecosystems and cultural sites along the way.