Diagram of the Vdara Hotel’s concave surface concentrating the sun’s light, from the Las Vegas Review-Journal
The Vdara Hotel on the Las Vegas strip has a simple, sleek, concave design. It’s curve gently cradles the hotel’s swimming pool, which was placed on the south side of the building to capture sunlight for as much of the day as possible. It turns out that it captures rather more sun than they really want, as the building can act as a massive solar concentrator, reflecting and concentrating light that shines down onto the pool.
And it’s not even as powerful as it could have been: the designers had included a film on the south-facing windows to scatter rather than concentrate most of the reflection. But the sun in Nevada is strong and it is such a large building that it still produces this spot that the staff have dubbed “the death ray” (management, who are less interested in stimulating the imagination, prefer to call it a “solar convergence”)
The article linked above gives the story of one customer who was sunning himself by the pool when he started to feel uncomfortably hot:
He tried to put on his flip-flop sandals but, inexplicably, they were too hot to touch. So he ran barefoot to the shade.
"I was effectively being cooked," Pintas said. "I started running as fast as I could without looking like a lunatic."
Then he smelled an odor, and realized it was coming from his head, where a bit of hair had been scorched. It was about 12:20 p.m., as best Pintas can recall.
Taking brief refuge at the pool's bar area, Pintas chatted with employees. He said they chuckled when he described what had happened. "Yes, we call it the death ray," he says they told him. Sometimes it causes disposable drink glasses to melt, a cocktail waitress added
When he gets back to his deck chair, he notices that the plastic bag he had left there has partially melted, especially around the black lettering (which presumably absorbs more of the heat).
The plastic bag after its tussle with the death ray; via Las Vegas Review-Journal
Now this is all accidental, but what if it could be used deliberately, could a sun-belt building be weaponized? What if the hotel’s exterior windows were all motorized and could be angled to direct the sun at various targets around the city. Built by a megalomaniac developer, the plan begins with just making the other buildings uncomfortably hot, driving up their operating costs and pushing competitors out of business (there were some complaints like that levelled against Frank Gehry’s titanium clad Disney Concert Hall in Los Angeles). Our enemy then purchases these defunct buildings and “retro-fits” them to add to his arsenal.
As people start to become suspicious, the attacks escalate to some murders, with charred bodies left and forensics can find no evidence of a fuel. Ultimately, as the net starts to close in on him, he unleashes the full force of his magnifying buildings, sending a fiery ray of energy to destroy important buildings around the city.