SOAP LAKE - City residents have been treated this week as someone carefully cobbled together stone structures on the lake's west beach.

And no one's really quite sure who's doing it.

"I live right there," Soap Lake City Councilwoman Kat Sanderson said, pointing across the street.

She went out for an hour or so last Saturday and came home after dark.

"And the next morning, there they were," she said.

"They" are cairns: stacks of rocks and stones used throughout the world for centuries as memorial sites, trail markers, art sculptures and more.

Soap Lake's collection steadily grew from nine Sunday morning to 18 Wednesday morning.

"The thing is, I've never seen anyone down here doing it. They just appeared," Sanderson said. "It's a mystery."

"But it's the mystery that makes it fun," local artist Brent Blake said.

Sanderson said her neighbors are bewildered as there's been no sign of people stacking the rocks.

And some of the stones are so precariously balanced, it's unlikely the work was done overnight with little light.

Sanderson has reported no unusual lights in her neighborhood, and suspects more than one person is involved.

"Some of those are pretty heavy rocks, so it would have to be a couple of people," she said. "And a lot of them are balanced, so you know nobody's just throwing them together."

A few may have been too balanced: after the initial 9 were discovered, two more appeared Monday morning.

Tuesday morning, two had been discovered toppled. Come Wednesday morning, the number doubled to 18.

Blake added his own Thursday morning.

"We're all looking forward to what happens next," Sanderson said.

"I'm hoping that the same people who were building them are sneaking down to do more," Blake said.

"It's another weird, wonderful thing for Soap Lake. That's what Soap Lake's all about," he said. "There's some cool stuff going on here."

Sanderson said she'll continue to check in on the cairns as long as they're standing, which Blake hopes will be a long time.

"It'll be so much fun watching these things continue to propagate," he said.

City Councilman John Glassco called the structures a phenomenon that could only happen in Soap Lake.

"What a neat thing to happen right here with all these rock just hanging out," Sanderson said. "Somebody moved them and turned them into something."