The Godless City

To remind all men that fortune is never constant, a storm afflicted the victors of the great naval battle so that within an hour they might have wished to have lost it instead that retreat could save them. Of one ship tossed far and then low, sinking, an officer and a portion of his soldiers made the shore.
The officer declared it a miracle and vowed to give offerings to the god who preserved them, and if there was no shrine for the purpose already, he would have one made, and the same for a temple when his means permitted. He encouraged his men to join him in that. "Certainly, but what god is it?" they asked.
The plain and uninhabited shore gave no answer to that. Stymied, the officer led his men away from there and succeeded so well that not a single one of them died before seeing home or whatever other destination he liked.
That duty done, the officer turned to the other, and in furtherance of it he settled a colony where he washed up. It flourished, whereupon the founder attracted scholars and philosophers whom he tasked with determining the god in addition to their other studies.
It flourished still more and soon became prosperous enough that its founder had erected the grandest temple known, though he refused to have it consecrated before his rescuer was known. More than that, he forbade the building of any other temple within the city limits before then. The injunction is observed today. Therefore, stranger, to answer your question at last, your devotions must be done outside the walls.
Finis