Just back from Athens. If you are thinking of renting a car at Athens Airport, stay away from GreenMotion. It's a mess. The problem with it even not that it doesn't have an office at the airport - the problem is that it cannot organise transfer to its office some 20-25 min away from the airport. After we had spent four days in Athens, we had a scheduled car collection from GreenMotion's "airport" office, specific date and time. As we were supposed to, we spotted a GreenMotion staff member at a certain exit (which GreenMotion keeps calling a "gate" - confusing, but never mind) in arrivals, who couldn't explain anything about further logistics (how, when, how soon or how long) - and not only because the poor guy did know a word in English, but mostly because he and the company had obviously not expected us to come pick up the car. For some reason he made us follow him from arrivals to departures, to car parking, and back until we returned to the terminal only to keep waiting with no information. We finally arrived at GreenMotion's office after 1.5 h of waiting and wandering inside the terminal. The reception officer did speak English, but instead of offering apologies, she rebuked me for not sending them an email to confirm that I really wanted to pick up the car at the hour I indicated in the original booking. "I am giving you a special responsibility-waver rate and a very big, brand new car", she said. The rate turned out to be the usual one and the car was exactly the economy type I had booked (of course not "very big") and it was not new. Since I bought the waver, I suggested I leave the car at the airport departures for GreenMotion to collect it once the rental is over. And remembering our unfortunate experience, I sent several emails to GreenMotion ahead of the return date. No surprise, I received a reply that neither bothered to confirm car collection at the airport terminal, nor explained any details of their preferred way of receiving back the car. Intuitively, and in order to avoid a very likely mess at the terminal, we figured out that returning the car to the office very well ahead of the schedule should work out best with this company. We were right. But only for ourselves, because the only staff member at GreenMotion's office, after having had me to sign several papers in Greek, locked the office and drove us on the same car to the airport terminal. So whoever arrived at GreenMotion's office after us, they only came to bounce against a locked door. Not recommended.