Ok, firstly you make two trips to the spire fyi.
First trip is a 10yr+ trip timewise and you spend a large amount of time there. Upon your return you will then come across Bloodstone and Wraithmarsh - and trust me, they are brilliantly done. I can't say any more obviously.
Your second trip is the endgame trip obviously.
Any existing quests will be still with you after your first spire trip.
I finished the game last night. The ending wasn't the best I do admit, but overall I really am hooked on the game still. At first I hated Fable 2 and I couldn't get to grips with its cartoony nature and humour. It isn't perfect by no means but an interesting take on the RPG genre.
9/10 for me.