Hi and welcome to the forums,
I am suggesting not to miss visitng Knossos, Phaistos, Gortys, Malia. The arcaeological museum of Heraklion.
The castle Koules in the port of Heraklion, part of the fortification of the longest ever siege in history.
If you travel to the east make sure you visit spinalonga island.
Also to the east there is Chania, probably the most beautiful city of Greece, and even more western, some of the most beautiful beaches like Falasarna, Elafonisi, Balos, Sougia, and Loutro. Samaria gorge is also a must.
I surely missed a lot, but I think covered the basics but I think you can do also a little research on your own about the places I told you, and maybe come back to give you even more info
Yes, it's not easy to recommend places without knowing your priorities - e.g. archaeology/beaches/scenery/walking/hiking/waterparks/clubbing etc etc.
I strongly recommend that if you are staying for 3 weeks, you have plenty of time to stay in 2 or 3 different locations, which I think would be a good idea..
I'm guessing that your asking for suggestions re attractions and places to visit means that you don't yet know very much about Crete, or about what this Great Island (as it has been known for centuries) offers, and that you therefore don't yet have priorities. At this early stage of your planning, what would be of most help is not other people's opinions, but spending some time doing a bit of background reading. There are several guidebooks to Crete: the Rough Guide and the Insight Guide are especially good, I think.
Gerlion has given you some good ideas, and he and Steve both recommend that you have two bases, or even three. Because Crete is so large (it's the Great Island size-wise as well as history-wise, landscape-wise, and every other-wise) and the distances are so deceptive, I think they are absolutely right. But perhaps you have a non-negotiable reason for wanting to staying the entire time in Heraklion (staying with friends or relatives for example?) If that's the case, Heraklion is probably the best place to stay, since it's bang in the centre and the best starting point for reaching the far east and the far west, and points between, plus most of the main historical and archaeological sites. It's also a very interesting and rewarding city - much more to it than the complaints about the traffic would lead you to believe. (It's a city, after all!)
To give you an idea. it will take you about an hour, perhaps a bit less, to drive to Rethymnon and 2 hours to drive to Chania; another hour to Falassarna, and 1.5-2 more hours to Elafonisi. Driving east, it will take you a good hour to drive to Agios Nikolaos and another 2.5 hours to drive to Sitia. So a good 7-8 hours between the far east and the far west. And if you want to go to the South coast, you need another 1.5 hours from Chania to Chora Sfakion or Paleochora or Sougia (the only villages that have roads) or an hour from Rethymnon to Plakias.
That gives you a baseline for your trip planning, but I think you could make better use of your time than to spend so much of it in the car! It would definitely be better to have two or three bases, but there's no point in suggesting the other base(s) until you've (a) told us more about yourself and (b) what interests you. So your next step is to read, make a short list of the places that appeal to you, and then once you've got to that stage, come back with some specific questions.Edited: 29 July 2013, 14:24
It also depends on your style of travel. If you pack light and don't mind moving from place to place, you could easily expand your number of bases to 6 or 7 if exploration is more of a priority than relaxing on the beach.
Another major consideration for having 2-3 bases is that petrol is dearer in Greece than it is here so you need to minimise backtracking as much as possible. So, sit down for a couple pf hours with one of those guide books and make a list of the places/sites/attractions/towns, etc that appeal to you based upon your preferences. It's no good us telling what to do until we have an idea what you would like to see and do. Three weeks is a great time to have, but you will still need to make a list and stick to it, or else you will end up spending the majority of your available time in the car.
If you do want to see a spread of sights across the island, then you could, as somewhere to start, consider mayeb Agios Nikolaos, then either somewhere around the Matala or Plakias areas on the south coast for base #2, then back to the north coast to Chania in the west
The distances are large, but I think the timings given above for Sitia are too long. The bus from Ag. Nik - Sitia takes 1 hr 45m;
Maybe the road has been significantly improved in the last few years.
Yes, I should have said (I intended to in an edit, but time ran out on me) that my guesstimates of driving times might be out of date, as it's many years since I've driven the roads in the eastern part of Crete. I wanted just to give Kate a rough idea of what she might expect, and encourage her to decide on another base or two - partly because of GB's observation about petrol, the cost of which will mount up astronomically if they stay in Heraklion but want to see most of the island, but mostly because although the roads of Crete are beautiful and exciting, they'd have a better holiday if they didn't spend half their time sitting in a car.Edited: 29 July 2013, 22:51
Wow thank you so much everyone for your ideas!!! I have read through a couple of guide books - that was a great idea! I'm so grateful and I can't wait to get going now!!!! :)
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