A
Caves (洞穴) have a primary appeal — they hold the secrets to our past and are mysterious in and of themselves.
● Mammoth Cave
Kentucky, USA
The longest cave system in the world lies beneath the Green River Valley in Kentucky and while over 400 miles of passageways have been mapped, it has yet to be fully discovered. The complex limestone labyrinth (石灰岩迷宫) was discovered by humans 4,000 years ago.
● Blue Grotto
Capri, Italy
Once used as the personal swimming hole for the Roman Emperor Tiberius, this extremely bright sea cave is almost 200 feet long and 82 feet wide. Its unique glow comes from the light entering the small opening to the outside.
● Avshalom Cave Nature Reserve
Beit Shemesh, Israel
Also known as the Soreq Cave Nature Reserve, Avshalom is considered to be the Rosetta Stone of climate history in the Eastern Mediterranean through the packed stalactites (钟乳石) found in the cave, some of which are over 13 feet long, and are as old as 300,000 years.
● Cave of the Crystals
Naica, Mexico
This unique cave system in Mexico contains some of the largest natural crystals (水晶) ever found—the longest of which is 39 feet long and 13 feet thick. However, it is rarely explored due to logistical difficulties: it is extremely hot due to its location above a volcanic vent, and the huge crystals block also block the passage.
21. Where does the longest cave lie in?
A. Kentucky, USA. B. Capri, Italy. C. Beit Shemesh, Israel. D. Naica, Mexico.
22. Av shalom is famous as .
A. the most beautiful cave. B. the Soreq Cave Nature Reserve.
C. the Emperor’s swimming hole. D. over 400 miles of passageways.
23. Which cave includes the largest natural crystals?
A. Cave of the Crystals. B. Blue Grotto.
C. Mammoth Cave. D. Avshalom Cave Nature Reserve.
