An ancient royal site on the plains of County Roscommon in Ireland.

Many prehistoric and early medieval earthen monuments (mounds and raths) were found here.

According to legend , Rathcroghan was the seat of King Ailill and Queen Maeve of Connacht , whose pillow talk led to the old Irish epic , "Tain Bo Cuailnge (The Cattle Raid of Cooley).

The limestone cave , "Oweynagat" (Cats Cave) , with two "Ogham" stones , was thought to be an entrance to the underworld.