The Christian basilica at the heart of Tigzirt is one of the better-preserved early Christian monuments on the Algerian coast. Dating from the 4th or 5th century, it was built at the height of the town's prosperity as the Roman port of Iomnium, and its floor retains sections of geometric mosaic work that have survived remarkably well under the Mediterranean sun.
The basilica is a three-nave structure typical of North African early Christian architecture, modest in scale but significant in age. It sits close to the ancient forum area, and the surrounding ground conceals further Roman remains — column drums, carved stone fragments, and the foundations of civic buildings can be seen along the lanes of the old town. Entry is free and the site is unfenced; the mosaics are visible without specialist guidance.