My wife and I visited Budapest early this year and had an incredible time. The parliament building, of course, was a major highlight.

I also recommend:

• The House of Terror: A museum containing exhibits from the fascist and communist regimes which dominated Hungary for decades. https://en.wikipedia.org/wiki/House_of_Terror
• Memento Park: An outdoor park where all of the Soviet era statues from Hungary were collected after the fall of the Soviet Union. https://en.wikipedia.org/wiki/Memento_Park