Heraklion is the reputed center of the Minoan Civilization. Read up before you go, then marvel at such wonders as the Palace of Knossos. The island itself lends an aura of mystery and ancient civilization.
When visiting the Greek Islands, leave time in your schedule for mainland Greece. There is a myriad of reasons to visit Greece. The most important by far, is the people. Warm friendly, earthy, family centered, are all words that describe the Greeks. Spend some time with a Greek Family. You will bring back memories you will never lose. While you are at it, take in the marvels of an ancient civilization you have only read about until now.
In closing, let me implore you to seek advice before you go. Brochures are made by companies who are paid to make a resort or destination look tantalizing. Educated Travel Agents can pair you up with the proper resources to give you honest information, and trustworthy advice.
Travel Well my friends.