Christmas markets are a German tradition for the pre-Christmas period dating back to the Middle Ages. Therefore there is nothing more authentic than the Medieval Christmas fair in Munich.
You can call it a themed Christmas Market, it is actually a Christmas market like all the others, only that not much has changed since the medieval times: there are people walking around in medieval costumes, knights, merchants and ladies; you can enjoy delicious food and drinks prepared like there were back in the Middle Ages and buy cute original presents, such as handmade jewellery in medieval patterns. Or simply wander around and let yourself get lost in time.
Don’t forget to check their website for the actual programme, as there are also events, such as medieval theater plays, medieval dances or concerts.