If you want pretties, Frozen Niagara (Domes and Dripstone) is your best option. The historic tour is just that - along with big passage. The Wild Tour gets off the usual tourist routes. Note that there are some odd requirements (like boots with laces) for that trip. I'd suggest taking the longer versions of any of the tours since a lot of the time is eaten up on the bus ride to the entrance. It is quite possible to book multiple tours (say one in the morning and another after lunch) on the same day - and, if you're going to be there for any length of time, I'd recommend doing that.