We arrived in Athens two days prior to embarkation, so we could see the sights, and had a marvelous time, not a HAL excursion, but taken about by Constantine with AthensTaxi.org. This is a family run taxi/tour company that will go out of their way to show you the sights and a good time. He picked us up upon our arrival at the airport at 9:AM, took us to The Athens Gate Hotel, where we checked in, checked our luggage since the room was not yet ready, and we went on a 1/2 day Athens tour.
I admit to being awed by the ancient ruins, as I studied classical Greek in high school, but this was my first in-person exposure to the area. It was super-hot on the acropolis, but we took our time and saw everything - Parthenon, Temple of Athena Nike, looked down on both theaters from above, took a zillion photos - then went to a great casual outdoor restaurant near the agora for a gyros lunch with fresh feta & tomato salad, and tried to local beer. The beer was probably a mistake, after a long flight, no real sleep, and the heat on the rocks, began to be very tired.
But, we sucked it up, toured the agora, then took a drive up Lykavittos Hill, stopping for several views of the area below. After a tour past some of the important government buildings, the university, we drove thru the main downtown business area, and then back to the hotel.