So far I've managed to make it fairly far through the main story with decent map completion without ever entering a dungeon, but while reading through all of the mails I've collected for completing various renowned and personal story quests I have noticed I've been collecting a variety of mails whose icon is a 'door' - I am assuming that these are dungeons.
Looking at the map I have noticed I have a couple of these appearing in relation to the mails, which I am assuming are dungeon entrances:
What are the locations and level requirements for each of the dungeons? Do all of the dungeons follow on from a specific part of the story, and are these affected by the choices I make during my personal story?