The Frick Collection—the World’s Favorite Museum—has reopened after a five-year renovation and expansion. Here visitors will see many of their favorite masterpieces lining the walls of the spectacular 5th Avenue Beaux-Arts mansion built by industrialist Henry Clay Frick during what Mark Twain would name The Gilded Age. They will also see new galleries in the family quarters on the mansion’s second floor, which is now open to the public for the first time in its more than 100-year history.