St Mary’s Abbey goes all the way back to 1300, when it was built by the O’Reilly clan. Today’s remains include a three-storey bell tower, a section of the west wall, and a graveyard, where the great and the good of Cavan have been buried for centuries. They include Eoghan Roe O Neill, a leader of the 1640 rebellion and Myles "the slasher" o’Reilly, hero of the 1644 Battle of the Bridge of Finea.
