Concrete crop circle ?

Know I have seen this before but can not think of what it is there for.

Decoration. The architect got tired of drawing straight lines.

Fancy control joint?

I was thinking patch for a BBQ pit perhaps or something related to sports but can’t put my finger on it.

Roundabout Joint Layout…

Marcel I do not understand half the lingo in that PDF.
Can you explain in English?

Has to do with minimizing a shrinkage crack and not just controlling the crack in a straight line. The same thing happens in sheet metal with a small crack (stress riser). The way to stop the stress riser from getting worse, is drilling a round hole at the end of the crack.

A ‘round about’ is a traffic circle in North American English, a free flowing intersection for roads. I don’t think they have anything to with circles in patios.

It’s of course a solar collector that when viewed with a high pixel Thermal imaging camera should make it readily apparent. Could also be an old fountain feature that was removed prior to the solar collector having been installed… Maybe a crypt… or a burial ground of Native American origins.

It’s an old fire pit that’s been filled in

Maybe Hoffa

old septic tank or cistern underneath


Fire or BBQ pit was my first thought.

Would it not make sense that the patio base with the round glass table would Architecturally fit aesthetically in that round about pattern?:slight_smile:

I was thinking fire pit ring myself

Why? the concrete would be a different color if it would have been filled in at a later date. :slight_smile:

The coloring is a little off from the surrounding, but of course the photo is a little dark and hard to know for sure. I do agree that different pours at different time will have a difference in color