Archaeological museum, Fira
This is a very little museum, a display really, but it's worth seeing in my opinion. It's in the center of Fira by the huge line of people waiting to get on the funicular.
Rather than waiting in line, in scorching heat, for who knows how long enter the archaeological museum and see the great collection of pottery they have on display. It's very well preserved and they have notes in English about what each represents.
The entrance is three euro, a bargain.