Ned Stark's Head Wasn't the First to be Placed on a Spike
Beginning with the head of the notoriously rebellious Scot William Wallace (or who you might remember better as Mel Gibson in Braveheart) in 1305, the southern gate of the London Bridge served as a warning against betrayal to the crown.
Severed heads of those who were considered to be traitors were dipped in tar for preservation and placed out on the gate for all to see.
Though they were intended to be a displayed as an example of punishment, tourists came from far and wide just to catch a glimpse of the decapitated heads. At one point a German tourist counted 30 heads on display.
When the smell of decomposition became too much to bear for the surrounded shop keepers and bridge dwellers, the heads would be removed by an appointed "Master of Heads" and tossed into the Thames River below.