Bicycling tours of the city are popular in many European cities and areas. Bikes are typically included in the tour price and you don't have to be in super shape to complete these tours. Usually there are lots of stops and rest areas along the route.
Check to see what attractions the tour actually stops at, and does the guide provide a tour of the attraction or are you left on your own? Some tours provide a guide that stays with you the complete trip while others allow you to work with guides at the various attractions.