Now and again there are puzzles that involve being in certain locals in the real world to collect what is now know as “dead drops” (name given due to the first of these occurrences )
On the 11th of January this post showed up in the Niantic Project google+ page.
In the description there was a reference to lizard king’s doorway to the other side. This is a reference to Jim Morrison's from the Doors and to his grave
Later access to the video of the retrieval was given to us by the Damien Mórka
The content was given to us by Julien Lamy
There were some passcodes and invites hidden in the docs (images below)
The first ever reference to a dead drop and that would give the name for them during the ARG was the Chrome Industries one. Players were given 4 locations and had to figure that what was common among them was the Chrome Industries shops. In this case there were no posters as this only started for later dead drops.
More info here.
In all these coordinates there would be one poster in the zipcar shop that could be redeemed for items in Ingress.
This was also the very first appearance of Hubert Farlowe.
Using the Operation Juice Club document as a start we can determine there is a dead drop in some Jamba juices shops (see below for estimate of their locations)