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.