First time in Berlin

Hi all,

After a crazy year or so at work, my wife thought it best to get me to look up and enjoy the world for a bit. We are planning to go to Berlin near the end of May. Any thoughts on must dos / must sees would be much appreciated. We have enough time that we could do the "off the beaten track" visits as well as the more customary attractions. Oh, and watch stops are more than welcomed!

Kind regards,

David