Go north to Maghera there are the ruins of St. Lurach's church and cemetary from the 10th century, built on the site of a 6th century church.  Get the key at the recreation centre and remember to return it, it is a honor to be allowed to visit this site.  There is a carving above the door of the last supper.  St. Lurach was married to the sister of St. Patrick and belonged to the Fir Li, if you are interested in ancient history of Ireland.  The burial plot of St. Lurach's is located here, although it was ransacked in the 1800's his presence is still there.

If you ask a local they maybe able to direct you to the site of the holy well, which has been covered over but there is a legend that there was a tunnel from the church to the well that people have been looking for for centuries.

Also just south on Mullagh road before you reach the Glenshane pass is a hill on the left, climb the hill from the layover on the north side and be treated to the Old Mullagh church ruins and cemetary, no one knows much about this site but from the layout it looks like the original home of a rath or fort.  Perhaps dating back thousands of years, it commands a view in all directions. 

These are ancient and sacred sites and a priviledge to see. 

The Carntographer website has more information on a sweathouse, dolman (under excavation by archeologists at the moment) and other sites of antiquity in the area.