Jeff & I just back from our second cruise, and our first on the Celebrity Century. We had an insider cabin on the highest passanger deck, which is the 12th. That turned out to be an ideal location in that the Islands Cafe was directly below us, and the Grand Dining Room was an easy journey via the very accessible and user friendly inside staircases.
I don't want to duplicate what others have already said about this ship and itinerary, so I'll give just a few comments.
I highly recommend booking a private two day tour with the independent tour company Red October. Also, I highly recommend our tour guide, Julia, who was a wonderful tour guide who actually grew up near Peterhof, and still lives there. The price of the two day private tour came to $747 per person, which is less than half of the cost of a one day tour booked with the ship.
Cabin 1217 is an ideally located insider cabin because it is on the top deck of the ship, and is very near the action, so to speak. Also, you receive a very high level of individual service from the room attendants because this cabin is located in the middle of a bunch of expensive balcony cabins. In addition, because it is an inside cabin you can easily take restful naps without the daylight keeping you from being able to sleep during the day. Also, one of the best features of any of the cabins aboard this ship are the superb showers, which never ran out of hot water, and actually got hotter the longer you had them on.