In the winter months in Greece, a great 2nd base would be NAFPLIO ... just 2.5 hours on a modern highway rom Athens, but feels like a world away.. It's a protected Heritage Old Town, on the tip of a peninsula, surrrounded by the sea. Gorgeous Italianate Archictecture, a Marble-paved central square, chic shops and cozy tavernas (restaurants). It's lively all year long, since it's a real city --- with a large "new town" to one side, and a locel university. In the winter season there are Holiday festivals and cultural events. There's a long seaside promende with canopied cafes (they have clear plastic siding, so people can sit out in comfort even in December ! It has several fine museums as well. Always lively because year-round this is a favorite weekend getawaay for savvy Athenians.
This superb NONcommercial website - http://www.visitnafplio.com/ tells ALL ... how to get there, where to stay, most authentic places to dine , local highllights etc .And here's a sampling of highlights, in Old Town & nearby, in warmer months, but it gives you a idea of the surroundings. https://www.flickr.com/photos/stanbr54/albums/72177720319228274/
.It's super-easy to get there on fast modern KTEL ( intertcity) Busses -- dep every 2-3 hours, heated, reserved comfy upholstered seats w footrests -- a scenic ride by sea, then thru rolling hills, citrius orchards. If you are in Athens first, Your hotel could call for timetable & reserve your seats. then you taxi from Central Ath to Kifissou St Bus Terminal in 15 mins for about €15.
If you feel driving its also a lot of fun -- especially if you drive straight from the Airport upon arrival, on the "beltway" that skirts athens, ---you dont even tap the brakes until you're over the Corintth Canal. Many ancient sites near Nafplio are fun--- just be aware that in Winter, some of them close at 3 pm and most will be closed Thurs xmas day & Frday Dec 26. ... Plan Ahead. A possible plan: fly in Saturday Morning, drive to Nafplio for Sat -Sun- Mon.. then back to Athens Airport to tlurn in car, then taxi to a central Athens Hotel. If you decide aganst driving, you can just take an X93 bus for 6€ from Airport in about 50 mins, to KIssifou Bus Terminal