That Alan Furst about the eve of WW II and the escapees, I love it, but it has NOTHING to do with today's Thessaloniki ... a big busy trafficky, concrete city, hard to find the feeeling of the past, most people who choose it on a first trip are scholars of Alexander & Phililp II, to see the royal tombs at VErgina but I doon't think that's you. U haven't done enough research that's all.
I agree with others that with only 6 days, you can get "the most Greek bang for your buck" by combining Athens & the Argolid area, specifically NAFPLIO. It's considered THE most beautiful Old Town in Greece, gorgeous golden Venetian architecture, on a peninsula, surrounded by the sea, so feels like an island, in the middle of THE most historic area in GReece (Iliad-Odyssey Land), and ALSO has gorgeous beaches, plus nightlife, vineyard... AND it's only 2.5 hours away on the most modern highway in GReece. Do this first, then come BACK to Athens & it will mean much more to you.,.. and besides, with 3 days in GReece, you'll be more savvy about handling the big city & its famous landmarks will mean much more. This superb noncommercial website gives ALL info about Nafplio & surrroundings - http://www.visitnafplio.com/ a WEALTH of info and reliable, NOT puffery.
Here are 2 wonderful Albums to show you the beauties of Nafplio area AND the historic central Athens Landmarks:
NAFPLIO - http://www.flickr.com/photos/stanbr54/sets/72157632094108982/
ATHENS - http://www.flickr.com/photos/stanbr54/sets/72157632121475515/
This tested Itinerary, is travel-efficient, minimizes transit, avoids backtrack, maximizes time enjoying. Use This MAP http://euro-map.com/karty-grecii/peloponnes/podrobnaya-turisticheskaya-karta-peloponnesa.jpg It is GOLD! Shows all roads right from Airport to Peloponnese & Nafplio AND back, all u need to plan. Click & it gets huuuge, & navigate using sidebars.
FIRST - try to get a flight that's nonstop from N. America AIRCAn, Delta, USAIR -- yes it will cost more, but these are the ONLY flights that land between 9 - 10:30 AM on 1st day. When your visit is so cruelly short, you must spend more $$ to add precious hours.
• DAY 1 - Arrive 9:30? Drink strong coffee, Rent car & be out of Airport by 11 am - 4-lane highway, NO stops until after the Corinth Canal. About 15 miles on, Jump off & go 5 miles for 60 mins to visit ANCIENT NEMEA, an Olympics "wanna-be" was a Sacred games site, stadium, theatre, the works! Arrive Nafplio, by 3 pm? take nap to recover from ttrip, then wander town, enjoy sunset! I think the sunsets at seafront cafes are better than any in Greece.
• DAY 2 - Up early to MYCENAE to beat the bus tours... then back to NAFPLIO... go up on Acronafplia? Walk around the "point" at sea level to Town BEach ... Don't miss small superb Nafplio Arch. museum on square. Enjoy nightlife!
• DAY 3 - check out, drive up backroad of PALAMIDI (the FOrtress atop Gibraltar-lke rock behind town), take amazing pix. Then drive EAST across " THUMB" of Peloponnese to ANCIENT EPIDAURUS. Lots of ruins but mainly its the stunning ancient THEATRE (read about it!!), afterwards, go on to the COAST. Stop for late lunch, a last dip in the sea, then drive N. to ISTHMUS. You can stop to see & photograph the Canal (SOO deep SOO skinny!). then drive to Airport to drop car. Bus or Metro to Central ATh hotel.
• DAYS 4-5-6 -- ATHENS Sightseeing. Get to Acropolis by 8 AM, and you'll beat the tour crowds... Read R Steves website here for good overview, and DOWNLOAD his FREE step-by-step audio guides to Acropollis, Ancient Agora, AND Nat. Arch Museum.