My girlfriend and I visited the Old Town Hall with the Astronomical Clock on our trip to Prague last year and we were extremely impressed with the magnificent views that we got to enjoy from the tower. We had the opportunity to admire Prague's beautifully lit landmarks and we easily got to the top of the tower by taking two different lifts, so I would say that the tower is disabled friendly. We also got a chance to see some of the beautiful interiors of the town hall, though having looked through some of the photos on TripAdvisor, I wish that we'd gone earlier during the day so that we could see more.
The beautiful astronomical clock is representative of the popular geocentric view of the Middle Ages, according to which the planets revolve around the earth, not the sun. The clock was installed in the early 15th century and it is the oldest working clock of its kind. It has several components: an astronomical dial showing the position of the sun and moon, statues of various Catholic saints and other figures, and a calendar dial. At the turn of the hour the figures are set in motion and this attracts large numbers of tourists keen to witness the spectacle by crowding underneath the clock. The clock was definitely one of the highlights of our trip to Prague and I wouldn't hesitate to visit it again the next time I/we go to this beautiful city.