Knowth is part of the Brú na Bóinne complex, a World Heritage Site that also includes the similar passage tombs of Newgrange and Dowth.

After its initial period of use, Knowth gradually became a ruin, although the area continued to be a site of ritual activity in the Bronze Age.

During the early Middle Ages, a royal residence was built on top of the great mound, which became the seat of the Kings of Knowth or Northern Brega.

The eastern passage arrives at a cruciform chamber, not unlike that found at Newgrange, which contains three recesses and basin stones into which the cremated remains of the dead were placed.

The right-hand recess is larger and more elaborately decorated with megalithic art than the others, which is typical for Irish passage graves of this type.

Knowth contains more than a third of the total number of examples of megalithic art in all of Western Europe;[citation needed] over 200 decorated stones were found during excavations.

However, the megalithic art at Knowth contains a wide variety of images, such as crescent shapes, and the oldest known illustration of the moon in history.

This suggests all manner of theories as regards the function of megalithic art within the Neolithic community who built the monuments in the Boyne valley.

Further, the recent excavations (1962 onwards) under George Eogan resulted in the erection of a concrete slab wall inside the mound's west entrance, restricting any investigation into the possible alignments.

Evidence for ritual consists of a large number of votive offerings found in and around the immediate areas of the timbers that formed the circle.

[5] In the late Iron Age and early Christian period, it became a hill fort with encircling ditches and souterrains added.

The same was found at the entrance to Newgrange, and the archaeologists there concluded that it had made up a white façade or revetment on the front of the monument that had fallen.

They also contend that if the builders quarried and brought the quartz a long distance, they likely would have used it to "maximum effect" as a striking façade, rather than laying it on the ground where it could not be seen as well.

[13] Along with archaeologist Carleton Jones,[14] Hensey and Twohig note that passage tombs in Brittany have similar near-vertical dry stone fronts, such as Gavrinis and Barnenez.