I'm looking at two different cruise itineraries, one of which goes to Heraklion, the other to Agios Nikolaos. Of course I wish I could see all of Crete, but that's not going to be possible. Which of the two is more interesting, which most Not To Be Missed? (I know that Heraklion is Knossos; I don't know what the main attractions are of Agios Nikolaos.) Thank you.