Knowth is a passage tomb commonly referred to as The Great Mound. Like Newgrange and Dowth, this is an older passage tomb that was built more than 5000 years ago. The mound was constructed before Dowth and after Newgrange. The Great Mound is approximately half a hectare (or 1.5 acre) which is similar in size to Newgrange. This great monument is 95m across and is surrounded by 18 smaller mounds. The entrances to the tombs use two passages that were constructed using banded stones, quartz, and granite.

The entrances to Knowth are located on opposite ends. There is an east and west passage. The eastern passage is roughly 40 meters long and the western passage is 34 meters long. The passage ends with a cruciform chamber that is 7m high. The mound incorporates smaller tombs, clustered around the mound, that are attached to the larger tomb.

Knowth, like Newgrange, is considered a World Heritage Site. Although there is no direct entrance to the mound, access is granted through a guided tour. The Brú na Bóinne Visitor Centre grants access to the mound and it is located near the village of Donore on the southern bank of the River Boyne.