Visit the empire state building (often) than any other skyscraper. which form of the modifier in parentheses correctly completes the sentence?

This sentence is a fragment, but grammatically you would modify 'often' with either 'more' or 'less'.

Example: "People visit the Empire State Building more often than any other skyscraper" 

Equally correct example: "People visit the Empire State Building less often than any other skyscraper."

The reality would be "more often" because the Empire State Building is very popular.