You can unlock this as early as DNA Sequence 10. To continue with “A Piece of the Puzzle”, you have to locate a total of 20 glyphs dispersed among the five cities. As you explore each city, you will eventually pass landmarks that will be added to your database. Some will have a icon, telling you that these buildings have a glyph on them somewhere. Locate the glyph, scan it with your Eagle Vision (hold ) and decode the puzzle presented. Do this for all 20 glyphs and the achievement will unlock.
Number of glyphs in each city:
- Florence - 5
- Monteriggioni - 1
- Tuscany/San Gimignano - 5
- Romagna/Forli - 2
- Venice - 7
Note: You can locate the glyphs in any order you want but the puzzles will always be in the same order as in the video below (or in any video you choose to watch).
I found this site very helpful in gathering the feathers and glyphs. For each city, it has location descriptions and a map. LINK
There is no way I would have earned this achievement without the internet. I was awful on the 3 symbol codes and the rings you have to spin to make the historic paintings/pictures. But after I got this achievement Assassin's Creed 2 became the second game that I have completed every achievement for.