I just returned from a cruise two days ago that went to Nafplion and Katakolon and also Corfu. You can walk to the main area in Katakolon as you dock right near the main street. We did not go on a tour in that town (we were taking a day off from all our tours) and just walked around for about 2 hours. Nothing much to see but a pretty harbour and lots of souvenier stands. Some decent restarants if you want a drink to relax infront of the harbour. As for Nafplion I don't remember there being much right near the ship. We took the Corinth-Mycenae tour and it was well worth it. The ruins are really something but be sure you wear comfortable shoes as you are walking on stones and uneven surfaces. Got some great pictures. Loved every minute. In Corfu we took the ship shuttle into town and just walked around the fort and town.
Both are great ports, but for trips to somewhere else. I suppose you could just walk around town and get the atmosphere, but you are in one of the cradles of civilization and IMHO it is a shame to miss the chance to see the sites.
Katakalon is the port from which you can visit the Temple of Zeus at Olympia, site of the original Olympic games.
Nafplion gives you access to Mycenae and many other ancient sites.
We just got back from back to back Med cruises on HAL.
Corfu - We did ship's tour to Achillion Palace- very good. We ended up in town and had some free time after a quick walk. We walked back to ship - allow 40mins. Ship has a shuttle to the port gate but then either taxi or shuttle bus (think 3 euroes ea each way) to town. Didn't get to the fort but we had seen enough forts in previous ports of call. Corfu is a nice town to walk around and enjoy.
Katakolon - We didn't go to Olympia as I had read on these forums that there was not much there and had seen bits on Cable shows about it. Friends went and said not much to see. We just walked the town - bought some nice clothes . Went for a ride on the 'train' they have that does a short tour (5 euros ea) - not much to see but town area is only a couple of hundred metres from ship dock. Just a port to chill out and some low key but nice shopping.
Katakolon - We didn't go to Olympia as I had read on these forums that there was not much there and had seen bits on Cable shows about it.
Interesting how different folks have different viewpoints.
We have visited ruins of all sorts all around the world, from Edinburgh to Egypt, from Ephesus to Cambodia! To me, Olympia was a special place to visit. It is a large precinct, and pretty well preserved (for ruins!) There are, of course, the ancient Games areas including the race track and the sports field as well as the remains of the lockers. There is the cauldron of the Olympic Flame from which it travels around the world every four years. Besides that there is quite a magnificent Temple of Zeus (the reason for the place and the games) which is also in ruins but interesting to visit, and a well preserved little temple built by Alexander the Great. If the history as well as the modern connections of this site are not inspiring to you, then I guess that visiting historical ruins is just not for you.