If you see just one ruin on Crete, see Knossos (in Greek it’s Κνωσός, stress is on the second syllable). The site is fairly compact, and much of it is accessible with restricted mobility. But 30 minutes will do it.
Greek island in the Cyclades36.406725.4333
(Χερσόνησος) — party capital of Crete in the summer35.3166666725.39
city in Crete, Greece35.33333325.133333
town in Crete, Greece35.5166666724.01666667