By... accident, you can see both the area inside and outside mosque Neratzes, the biggest of the four, if I remember well, mosques of the city. Today it houses the Conservatoire of Rethymno. Before 1657, when it became a mosque, it was a church.
The Venetian Rimondi Fountain, re-built in 1623, is in a corner among several shops, tavernas, cafes, and shops. It has lion heads and four columns with Corinthian capitals at the top and was a dependable water source in the sixteenth century. You can almost walk right past it without noticing, so make sure you're paying attention as you walk around!