I honestly cannot remember where all we visited in Santorini.  We took a day tour of santorini from a ferry from Crete and one day is not long enough at all.  When you get there, from a ferry port, I recommend that you take a taxi and do not care of how much it costs becuase if you try to walk up the mountian you will waste time and get a very bad sunburn of you are not prepared.  So, even if it costs alot, it is worth the purchase.  You must make time for seeing Akrotiri, it is an ancient site with alot of history that you should not miss.  If you plan to go to any of the beaches on the southern tip of the island do not waste your time with the white beach becuase it is not white sand like you would thing, it is just a buch of rocks.  It is great for taking pictures becuase my sister did get some very good pictures but it was disappointing otherwise.  Not to mention, a pain to get to.  The only way to get to it is by a very small boat, they refer to as a ferry.  There is no docking for that particular beach and you have to hop out of the boat and into wasit or shoulder deep water which is also annoying if you are carrying electronics like cameras with you.  We were not prepared at all for this becuase no one told us until it was time to hop out.  I do suggest the red beach which had a dock and looked so much nicer.  Be careful to pay attention to ferry intervals and times for picking up and dropping off if you are on a time frame.  Also be careful with taxi wait times if you are in a hurry to make a ferry back to Piraeus Port or any other island.  Realistically speaking, it is very hard to get to the ports just by walking.  You can if you must, but you need to be ready for the walk, the heat, and the time it will take.  Santorini is a beautiful Greek Island and it is a must if you are in Greece at all!