What is the proper noun for buildings?

There isn't a single proper noun for all buildings. A proper noun is a specific name given to a person, place, or thing.

Here's how you would identify a building with a proper noun:

* Buildings with official names: These often have proper nouns.

* Examples: The Empire State Building, Buckingham Palace, the Eiffel Tower

* Buildings with informal names: Sometimes buildings are known by a nickname or other informal name.

* Examples: The White House, the Pentagon, The Shard

* Buildings with addresses: You can use a building's address to identify it, although this is not a proper noun.

* Examples: 1600 Pennsylvania Avenue, NW, Washington, D.C. (the White House)

In summary: You need to look for the specific name of the building to identify the proper noun.