What is the tallest building in the world?
The current (2023) tallest building in the world is.

Burj Khalifa: located in Dubai, United Arab Emirates.

Interesting facts:
At 828 m [2,716 ft 6 in] tall, this building is more than twice the height of the Empire State Building.
It also has the tallest elevator in a building 504 m [1,654 ft]  
163 floors, the most in a current building 
Plus the loftiest restaurant at 441.3 m [1,447 ft 10 in]
What local laws and customs should an American citizen be aware of when traveling to the United Arab Emirates?