Plinky asked, "What famous monument do you hope to see one day?"
I'd like to go back to Mont St. Michel some day and spend more time there. I visited the place briefly during a trip while I was in high school, and a small part of one day simply wasn't nearly enough time to spend in the cloisters, much less the rest of the place. There's so much history there!
I would have been happy to wander up the winding road lined with shops at a leisurely pace had we not been on such a strict schedule, but as it was I was racing to make it to the top.
Of course, all visitors are on something of a schedule, because the tide covers the road to the island every day, and I'm not certain visitors are even allowed to stay past a certain time. It might be necessary to stay nearby and spend several days exploring, concentrating on a different bit of the island each time – the cloisters one day, different stages of the cathedral construction on different days, the shops another – to truly do the place justice.