The Archimedes Palimpsest is a medieval parchment manuscript, now consisting of 174 parchment folios. While it contains no less than seven treatises by Archimedes, calling it the Archimedes Palimpsest is a little confusing. As it is now, the manuscript is a Byzantine prayerbook, written in Greek, and technically called a euchologion.
To make this prayer book, scribes used parchment that had already been used for the writings of other books. They used a book containing at least seven treatises by Archimedes, a book with two speeches by Hyperides, fragments of a philosophical text most likely written by Alexander of Aphrodisias, fragments from a Life of St. Pantoleon, fragments from a Menaion, and two unidentified texts.
You can choose to view a specific work (i.e. On Floating Bodies, which is one of the seven works by Archimedes), or you can choose to view a specific folio (i.e. the undertext or overtext.)