Shard is located in southwestern corner of Wrothgar, just east from Friendship Gate, south from Siege Road Wayshrine.
Just like the name says “Beneath the ruined aqueduct” head to the ruins in this area. There are rather tall stone structures – Aqueducts. The shard is conveniently hidden behind one of the Aqueduct pillars. Be ready for a bit of climbing. Aqueducts and shards go well together it seems, since are more than one in this area.