The burial mound of Knowth, northwest of Newgrange, was built around the same time and seems set to surpass its better-known neighbour, both in the extent and the importance of the discoveries made here. It has been under excavation since 1962, and has the greatest collection of passage-grave art ever uncovered in Western Europe. Modern excavations at Knowth soon cleared a 34m passage to the central chamber, much longer than the one at Newgrange. In 1968 a second 40m passage was unearthed on the opposite side of the mound. Although the chambers are separate, they’re close enough for archaeologists to hear each other at work. Also in the mound are the remains of six early-Christian souterrains (underground chambers) built into the side. Some 300 carved slabs and 17 satellite graves surround the main mound. Human activity at Knowth continued for thousands of years after its construction, which accounts for the site’s complexity. The Beaker folk, so called because they buried their dead with drinking vessels, occupied the site in the Bronze Age (c 1800 BC), as did the Celts in the Iron Age (around 500 BC); remnants of bronze and iron workings from these periods have been discovered. Around AD 800 to 900 it was turned into a ráth (earthen ring fort), a stronghold of the very powerful Uí Néill (O’Neill) clan, and in 965 it was the seat of Cormac MacMaelmithic (aka Cormac mac Airt), later Ireland’s high king for nine years. The Normans built a motte and bailey here in the 12th century, but around 1400 the site was finally abandoned. Further excavations are likely to continue at least for the next decade, and one of the thrills of visiting Knowth is being allowed to watch archaeologists at work (although given the cramped conditions inside, you won’t be jealous).