Hidden in plain sight.

[Talroth]

Hide the symbol within other streets.

Build them as streets and alley ways that cover a nicely rounded hill, and each street or alley way has a convenient gutter that runs down the middle of it. All other street's gutters nicely bypass the shape's gutters/drop into covered sewers.

When it comes time to use the great summoning symbol or whatever, someone at a temple/hidden store house on the top of the hill takes an axe to a huge store of oil barrels, and sends a wave of oil down the gutters, gives it a good ten count (or whatever it would take for the oil to flow through a good chunk of it.) and then drops a torch on it.

Whoosh, magic symbol the size of a city. You can even hide the circle inside others that wrap around the contours of the hill.

[JDCt]

Thanks for the responses! I will look into doing several versions to see what I can come up with. I like the idea of using alleyways and perhaps not using main streets as my circle but the back streets and more sublte avenues etc... Here is what I came up with just using main streets and making a bunch of connections but it is way too obvious in myu mind still.

I was trying to disguise the circles etc as parks and public areas, and add in more streets and connections to keep the geometric thing going, but adding more confusion to the layout. I think I will have to do another version and maybe hide several smaller circles through out the city that are connected somehow. A bit more low profile...