GOTHAM SECRETS: Donna Karan discovered the key to New York City long ago, and she keeps digging into its treasure trove for design inspiration. Starting today, many others can go on a city scavenger hunt courtesy of artist Paul Ramirez Jonas, with nonprofit public art organization Creative Time and The City of New York. Jonas is unveiling city secrets with new art project “Key to the City,” which DKNY helps sponsor. New Yorkers and visitors can pick up their keys at a special kiosk in Times Square, which will allow them to literally unlock things across all boroughs, from a door on the George Washington Bridge’s pedestrian walkway to a Bryant Park lamppost light switch and a master bedroom closet door at Gracie Mansion. Those who don’t have the time for such an extensive tour need not fret, however. “DKNY PR Girl” — the Twitter alias of a DKNY publicist — will go on her citywide trip on Monday and plans to tweet about each discovery.