Monemvassia is 9 hours by ferry form Athens and has some decent hotels from A class down to tourist class.
It offers spectacular views and is a charming little place. It is a Byzantine fortress-town and it successfully resisted most attacks.
Many refugees from Laconia would come here in times of conflict.
In ancient times it was called Minoa.
The castle is well worth visiting and the sunsets wonderful. Also see Monemvasia