Koom Valley

And now Koom Valley stretched away ahead of Vimes, and he could see why he hadn’t made plans.  You couldn’t make plans for Koom Valley.  It’d laugh at them.  It would push them away like it pushed away roads.
“Of course, you’re seeing it at its best at this time of year,” said Cheery.
“By ‘best’ you mean – ?” Vimes prompted.
“Well, it’s not actually trying to murder us, sir.  And there’s the birds.  And when the sun’s right you get some wonderful rainbows.”

Terry Pratchett, “Thud”