1) The word "piano" contains three vowels: I, A, and O.

2) The construction of the Great Wall of China began in the 7th century BC and was completed over several centuries, spanning thousands of miles.

3) Mount Everest, located in the Himalayas, is the highest peak on Earth, with an elevation of 8,848 meters (29,029 feet). It is a popular destination for mountaineers and represents a significant challenge due to its extreme altitude and harsh weather conditions.

4) The word "book" contains two vowels: O and O.