Today's hidden gem is Monemvasia, Greece, a tiny Byzantine fortress on the Mediterranean that is being lovingly restored to maintain its original look-and-feel. It's like stepping into a time machine. Motorized vehicles are not allowed. In fact, they are not physically possible. All the building materials (except the local stone) are carried in on horseback or by hand, as are all other supplies.
Monemvasia is situated on a giant rock that is connected to the mainland by a causeway. At the top are the ruins of another town that once housed 20,000 people. The view is nothing short of breathtaking.
I don't normally do commercial plugs here, but I'm going to make an exception for the Likinia hotel, a hidden gem within a hidden gem. The exterior looks like a medieval stone building (and it is) but the interior has been recently remodeled and looks like a top-flight modern boutique hotel. The proprietor is a very friendly old Greek woman who I have no doubt takes very good care of her guests. Her English was not the best, but it was a damn sight better than my Greek.
If you do decide to stay here, pack light. You'll have to carry all your luggage several hundred yards over uneven cobblestone alleys and staircases to get here. But I promise you it will be worth it.