An image from lidar scans reveals the vast scale of the early medieval fortress beneath the forest at Castro Valente in Spain's northwestern Galicia region.Image credit: Castelos no Aire
Might have been Romano-Celtic resistance to the Visigoths. Galicia was Celtic in those days.
LIDAR is fascinating. I’ve been watching NatGeo docu’s on the finds in the Amazon via LIDAR. There is lots out there!