It's as if the 3 fingers of Chalkidiki, going east to west, become progressively more developed. Mt Athos, except for its 20 monasteries, is exactly as it has been since its creation as a peninsula in the northern Aegean. Sithonia, the middle peninsula, is much more developed, but still much quieter, and much closer to nature than Kassandra, the western peninsula.
As a side note, about 30 km north of Sithonia is Stagira, a beautiful mountain village and birthplace of Aristotle. Opened in 2011, Aristotle Park at Stagira has a statue of the philosopher, and lots of interactive instruments for kids, such as a solar clock, telescope, parabolic reflector, lens compass, pendulum and water turbine, all of which were mentioned in Aristotle's Physics.
Sithonia is full of hidden coves and private beaches, but also has its share of quality resorts and hotels. Sithonia is a little-known paradise and a favorite of Greeks. From its eastern shore the peak of Mt. Athos rises dramatically out of the misty sea, giving it the impression of a lost kingdom.
By the way, there are more than 30 campgrounds available on both Kassandra and Sithonia, for those who want to rough it and save some money. Inland on both peninsulas there are plenty of pine forests and hiking trails.
Sithionia's chief topographic feature is Mt. Dragoudelis in its center, which is also a nature preserve full of hiking paths. Other features of Sithonia are the ancient city of Toroni, settled in the 8th century, BC, with its church and fort, Porto Koufo, Greece's deepest natural harbor (the Germans used to hide submarines there during WWII), mentioned by the historian Thucydides.
South of Porto Koufo are the secluded beaches at the southern tip of Sithonia. Further north is Porto Carras, where the leaders of the EU met in 2003. Akti Oneirou (Dream Beach) features bungalows, camping, and one of the best beaches in Chalkidiki. It also has a laid-back night life.
The coast road of Sithonia curves through the forested hills, dips down to the sea and its many small resorts and camp grounds. Sarti, on the east coast, has a beautiful beach and a stunning view of the peak of Mt. Athos rising nearly 2,000 meters out of the sea.
Sithonia is a mostly undiscovered tourist's dream, and just a two-hour drive from Thessaloniki, a world-class city.