This is the number one attraction in Crete for good reason. The site is remarkable, although the reconstructions by the British archeologist Sir Arthur Evans are controversial. My own view is that they add to our understanding of the site, even if they are in places speculative.
Next stop was the Archeological Museum, which has many artefacts from Knossos and other Minoan palaces. Some, like this Bull are truly amazing.
Here a few of the weapon collections.
A short way across town is the Historical Museum, which starts after antiquity. Quite a lot on the Byzantine period, for which we don't have a lot of written sources. The WW2 section has plenty of information, well presented, but not many exhibits. The best section is the Venetian period and the siege of Candia, the Venetian name for Heraklion and the island as a whole. I hadn't appreciated how big the old city was until I saw this relief map in the museum.
There is a good room on the various revolts against Ottoman rule.
The one post WW2 exhibit I did like was this bell, converted from a bomb. The island wasn't short of metal after WW2!
Finally, the Venetian Sea Fortress down at old harbour. This has been extensively renovated, with a museum inside.
These are what is left of the galley sheds.
They have a few cannonballs left over from the siege!
For more on the epic siege of Candia, I would recommend Bruno Mugnai's book 'The Cretan War, 1615-7', published by Helion.