Nea Makri is a busy little seaside town about 45 minutes up the coast from Athens. I discovered it when I first came to Greece  to rent a motorycle over a decade ago. It is close to Marathon and numerous other ancient sites. It's also a good starting point from which to visit Thermopylae and Delfi. I stay at Villa Verde in Nea Makri which is very safe and the kind host, Chris Feather, is a wealth of information (and fond of beer like me).