A kafeneio is a place where old people used to gather and drink their coffee, play cards, later on drink some raki and who knows what else they could come up with to keep them out of the house.
Υpovrixio is a kafeneio like in those days, but you will find younger people as well (I hope I am still considered young!). It has a very relaxed atmosphere. You will also become relaxed if you drink some of the raki or ouzo and time will pass in no time. Eat something small as well to keep yourself on board (Ypovrixio by the way means submarine in Greek).
During summer but also during winter, as the weather tends to be nicer around here, mostly everyone sits outside. Ypovrixio is located next to a small square making it suitable for a nice outdoor hang-out.