King Arthur's Round Table, just south of Penrith, is a henge monument 90 meters across, originally having two entrances, though only one remains. It is enclosed by a bank and ditch, separated by a berm on which excavation suggests there may once have been a stone circle. A trench at the center of the monument had been used to cremate a corpse.
Near King Arthur's Round Table, but on the opposite side of the road, is another henge monument, Mayburgh, at its center one remaining stone of the four recorded in the 18th century as standing here. It's single entrance faces the Round Table, suggesting that they were built in relation to each other, and formed some kind of ceremonial complex. The entrance to Mayburgh also aligns with Blencathra and the equinox.
Later generations were able only to speculate about these monuments' origins. The association with King Arthur goes back to at least Tudor times, when the King's Antiquary John Leland, after visiting the site roughly between 1535 and 1543, reported that 'the ruine is of sum caulled the Round Table, and of summe Arture's Castel.' By 1777, the full name was in use, Joseph Nicholson and Richard Burn noting in their History of Westmorland and Cumberland that 'the country people call it king Arthur's round table.'
With regards to Mayburgh Henge, the local folklore surrounding it is pretty thin on the ground, but there is one tale, written down in the 18th century by an antiquarian who recorded that the locals remember not only the four stones in the center, but two stones near the entrance. The local tavern owner who owned the land removed the two stones near the entrance of the henge and soon after, the worker who removed the stones hanged himself and the land owner went mad and lost his wits. After that, no one thought it wise to go meddling with the ancient monuments after that.