Glass capsules were used to keep such giants in a “deathlike” condition which is similar to death, although they were not dead. At the time of its disappearance, this civilization had glass technology which is known to have altered the flow of time. The ancient technology had far more capacities than we believe. 30,000 years seemed like 30 minutes for those who were placed in the glass capsules. Not only humans but also extraterrestrials coveted this multidimensional technology.
The place when this glass capsules were located was covered with dark material up to 90 feet and was discovered during 19th century.