The Great Blue Hole lies near the center of Lighthouse Reef, a small atoll 60 miles east of the Belize mainland. It measures more than 1,000 feet across and 480 feet deep, and was formed by the repeated collapses of a limestone cave system formed during the last ice age. Mr. Harper recommends several remarkable properties in Belize, including Blancaneaux Lodge, Victoria House and Cayo Espanto Island Resort.