Complex sentence: In 1962, another entrance was built into the Caverns by blasting a shaft in the limestone and installing a large elevator at which time the natural entrance was also sealed off at the request of the Hualapai as it was considered a sacred burial place.
Split into simpler sentences: In 1962, another entrance was built by blasting a shaft into the limestone and installing a large elevator. At that time the natural entrance was also sealed off at the request of the Hualapai Indians as it was considered a sacred burial place.