If you really like factory fresh marzipan then you should visit the factory outlet - locals go there because it's the place to get freshly made marzipan. Niederegger is the best of all of them according to Mr. Nacho.
You can see some reviews here:
http://www.qype.com/place/77602-Nied...erkauf-Luebeck
Go there early - we always go there as our first stop after getting off the ferry from Denmark/Sweden. Mr. Nacho has a sweet smile on his face when he walk out of the factory shop and tasted the marzipan
The area is industrial - but then again why would they have a factory in the city centre. There is a Niederegger cafe in the city too but the price is not the same and again things are not as fresh - it's more touristy.
Niederegger's specialty in Mr. Nacho's opinion is the mixture of dark chocolate and marzipan. The toledo version is more shaped marzipan where as the Niederegger ones are coated with dark chocolate.
Hamburg is nice as a big city with a nice lake and canals. I like Bremen more because the buildings are more impressive.
Koeln is a nice city, with long pedestrian street and the cathedral is really impressive, Bonn is nice too, especially if you like Haribo. We went to the factory shop in Bad Godesberg and Mr. Nacho had the sweetest smile - more than our 3 kids
He said he had never seen such a wide selection of pick your own winegums and they were so fresh!