Blackwardine, Herefordshire, England is at grid reference SO 5300 5600 and in the parish of Humber.

It is the site of a Romano-British settlement known as Black Caer Dun. A golden bracelet and ring have been found there as well as many human remains. An 1885 account notes "broken pieces of pottery were thickly scattered about and in one part of the railway cutting near the surface some 40 or 50 yards of charred material 18" thick were observed".

It is where Alfred Watkins first made his discovery of Ley lines on June 30 1921. The place was excavated the same year.