The Renaissance Tower isn't in such an exciting part of Zürich. But you'll not be all that far away from downtown. That said, the Renaissance is near an interesting market called 'im Viadukt' The Marriott is pretty close to the Niederdorf, which is the touristy center of Zürich, which is actually pretty cool.

With your comment on the food, you really should head over to the Zeughauskeller, and get a nice Zürigeschnatzles and rösti or a schweinehaxen. Then you have the rest of your trip to burn off those calories! And a trip to Mövenpick for some ice cream near Sechselautenplatz is likewise advised.