Nafplio is 135 Km from the center of Athens. Should you want to visit this popular tourist destination in your own vehicle, it takes about 1.5 hours on the Athinon-Patras National Road. Exit at Nafplio.
Alternatively, you can catch one of the KTEL intercity buses which depart regularly from Kifisou station. You will reach the capital of the Argolida prefecture in about 3 hours.