Safe Passage is only available at the Sky Passage.
Tale of the Dragon
Safe Passage is also available at the Temple.
The sacred Sky Passages of Oranos were identified by the enemies of Atlantis as very dangerous buildings logistically because they could transport armies and Citizens instantaneously. These buildings were attacked and destroyed before all others. In response, Atlanteans becan building the Sky Passages more soundly and defending them from within. The Sky Passages were holy sites first and did not lend themselves to strong defense, the Atlanteans continued to rely on other structures and the troops transported by the Passages to defend them.