Knowth Passage Tomb in County Meath was built over 5000 years ago, probably after the construction of Newgrange and before the construction of Dowth. The Great Mound at Knowth is similar in size to Newgrange and is surrounded by 18 smaller satellite mounds. The Great Mound has two passages with entrances on opposite sides, the western passage is 34 metres long and the eastern passage is 40 metre long, ending with a cruciform chamber.

Knowth and the other megalithic sites of the Boyne Valley were designated a World Heritage Site by UNESCO in 1993.

Note all admissions to Newgrange and Knowth are by guided tour from the Brú na Bóinne Visitor Centre located close to the village of Donore on the south bank of the river Boyne. Guided Tours of Knowth are from April to October, the last Tour is 90 minutes before closing time of the Visitor Centre.