Natives of islands in the Pacific Ocean, such as New Guinea and Vanuatu, engaged in cargo cults in the years after World War Two. The War brought Japanese, Americans and the English into contact with peoples who had never before seen the type of technology they brought. The people on these islands were often gifted some of the supplies that the troops stationed on the islands received. As the war ended so did the arrival of cargo.
Some peoples responded by imitating the actions of the stationed armies. In different occasions they built imitation control towers, radios out of wood and attempted to flag airplanes into landing on abandoned airstrips, all to attempt to receive their own cargo.
The building of megaliths in Western Europe is a similar phenomena. My people, a race of IDTTers, once had a settlement in that area. Once my people left, the native neolithic people continued to built large circles of stones. Their motivation was to follow my people where they had went. In time this attempt at a practical action became part of their culture in it's own right.
And that's Stonehenge decoded.