Walk from Koenigsallee to Altstadt. Buy some Champagne Cake, Whiskey cake, Jordan Almonds, Champagne Truffles and other chocolates from Konditerie Heinemann. Walk to Alstadt. Not to miss are Fries with Aioli from Frietbox! Then take a boat down the Rhein to Kaiserwurth. Have Currywurst for the experience at Berliner Imbiss. If you're adventurous (and have prior bookings), take a train to Bochum to watch Starlight Express in German!