National Geographic Traveler magazine has named Thessaloniki in its "Top 20 Places to Visit" list for 2013. The city in Northern Greece is not on the radar for many casual travelers to Greece, but that may change. This year, it shares honors with places such as Ravenna, Italy and Marseille, France, along with Uganda and Malawi.
Thessaloniki is a beautiful city with a great Archaeological Museum and many local sites. It's a great base for exploring Northern Greece, and it has many international flights, making it an alternative gateway to Greece for many travelers.
National Geographic Traveler: Thessaloniki

Married to a Greek National for the past 32 years, own a home in one of the Northern provinces, and having spent three years in the military in the Northern Detachments, I can appreciate the history, architecture, and drama that played out in ancient Greece.
However:
One must keep an open mind and a well hidden wallet as some of the locals, because of the effects of austerity, are a bit put off by ‘visitors’ or foreigners. This is not to say, nor am I implying that travelling to Thessaloniki Greece is hazardous, but the traveller must be vigilant and stay aware of their surroundings.
I will be among the first to encourage a visit to the second largest city in Greece. Plenty to see and experience! I’m not sure what the nightlife is like as this wasn’t part of my life during the years I’ve spent in Greece, but I’ve read that there still is an abundance of Night Clubs, Discos and the like for those wanting to ‘shake a leg’.