Tonight I walked down to the intersection outside my house right at sunset. The sky was a wash of color: orange swept down over blue and purple, and the bottom of the sky almost clashed with the green color of the grass.

I decided to follow the loop around but, wanting to be contrary, walked in the opposite direction from the one-way arrows directing vehicle traffic. After all, I was walking, not in a car.

The top of the sky was becoming striated with navy blue and black, so twilight was almost over when I saw it: a perfect circle of white against the darkening green of the grass.

And I mean a perfect circle. It was really too perfect to be natural. Even mushroom tops are really actually ovals.

I couldn’t resist going over to see what was in my neighbor’s yard. As I crossed the street, a car with a checkered pattern on it turned a corner onto the road — a taxi. Concentrating on my errand of curiosity, I barely paid attention.

Halfway across the street, I heard brakes squeal, but fortunately I was able to get out of the way. Unfortunately, the passenger in the taxi turned out to be the neighbor whose yard I was investigating.

He advanced toward me. “What are you doing?”

I pointed. “There’s something on your lawn. A perfect circle.”

“So? What business is that of yours?”

“It could be something dangerous,” I said nervously. It really could have been anything, and I knew it was a weak excuse. Our neighborhood is pretty laid-back but, well, trespassing is trespassing.

And my neighbor knew it. “I think that’s my problem. Why don’t you go on home.” It wasn’t a suggestion.

Figuring I could come back and inspect the mysterious circle later, I didn’t press the point. I had just gotten back to the street corner when I heard a noise behind me.

Turning around, I saw that the circle was rising out of the grass. It stopped about an inch above the top and then started to rotate. Water spiraled from the edges.

I had gotten overly curious about a sprinkler head. It was an ordinary, run-of-the-mill item that could be on anyone’s lawn — and was certainly nothing to wonder about.

Maybe I have an over-active imagination. But I’m going to blame the twilight.