We recently completed Empires of the Med and made the same tongue in cheek comment about ADA. Lots of walking and steps and standing for long periods of time. There were clearly folks on excursions with mobility issues who were unable to keep up. Some in our group were complaining of aches and pains after a few tours. Do not understand why Viking does not offer slower pace tours as they do on River. That being said, please be realistic about your capabilities as it is not good for you or your fellow travelers to attempt activities beyond your limits.