Conversation so far:
what is the tallest building in the northern hemisphere
Burj Khalifa is the tallest building in the Northern Hemisphere.
what is the tallest building in the southern hemisphere
Q1 is the tallest building in the Southern Hemisphere 2018.
what is the tallest building in the eastern hemisphere
Burj Khalifa is the tallest building in the Eastern Hemisphere.

Question: in the western hemisphere
Self-contained rewrite: what is the tallest building in the western hemisphere