We hesitated at booking a tour that included the Terrace Houses, but are very glad we made the effort to see them. My husband has a touch of emphysema, but was able to climb the inside stairs with only one or two difficult spots where there were more stairs. Totally unexpected was the difficulty I had taking the descending stairs outside. They are stone/marble, with a much higher rise than what we're used to taking. No hand rails. My husband walked in front of me to steady me, as I have arthritic joints and hip bursitis. If you take this side trip and have any joint problems, be sure you have a "buddy" to help you. Having a private guide rather than taking a group tour allowed us to take the time we needed.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.