Pyrgos is located on the northwestern side of Gavdos (about 6 km from the ferry port). It comprises in fact a pair of beaches with golden sands and crystal clear waters that are "hidden" below the cliffs. Access is accordingly relatively difficult, down a steep path.
In other respects the beaches are beautiful and offer complete isolation (without any infrastructure).
If you visit, be sure to bring along the necessaries (water, food and so on). One walks here from Ambelos, a hike of about 2-2.5 hours.