The history of mosaics

Ancient Greek Mosaics & Designs from Pella, Thessaloniki & Crete.

Bardo Museum Mosaics, Tunisia

British Association for Modern Mosaic

Byzantine and Roman mosaics, a photo album.

Byzantine Mosaics, a photo album.
Wikipedia entry on Byzantine mosaics.

Classical Mosaics

The Joy of Shards
Mosaic gardens, Mosaic sculpture, London mosaics, La Maison Picassiette, Chartres, France, Niki de Saint Phalle’s Tarot Garden, and others.

Nile mosaic of Palestrina
The Nile mosaic of Palestrina is a late Hellenistic floor mosaic depicting the Nile in its passage from Ethiopia to the Mediterranean.

Palestrina, a guide.

Pietre dure. Wikipedia entry.

Pitti Adami Mosaics

Roman mosaics in Sicily
Roman mosaics, a gallery.

Villa Romana del Casale, Sicily,
the richest,largest and most complex collection of late Roman mosaics in the world.

Wikipedia entry on Mosaics.