Lovers of mosaics will be dazzled by the glittering gold scenes in the 11th-century main church here, a listed Unesco site. The work was likely done by craftspeople from Constantinople, showing the fluidity of styles between here and the Islamic Empire. In the apse are portions of geometric decoration of the kind popular in Islamic buildings further east – just as, say, the Umayyad Mosque in Damascus features Byzantine-style gold-backed mosaic scenes. Pay attention to the opening hours.
Restoration work is nearly complete. When the Ministry of Culture takes control of the finished project (at an unknown future date), the site is expected to be open six days a week, with an admission fee. Confirm details with the tourism office before you leave Athens.
It's possible to combine a visit to the monastery with one to Elefsina, as they are on the same A16 bus line (departs from Agia Marina metro stop); you can also take the 866 or 811 from Koumoundourou. On the access road to the monastery are a decent cafe and a free, shady botanical garden.