"So, going anywhere over the holiday?"
"Yeah, I'm going to the K-T boundary."
"Woah, isn't that, like, in time or something?"

- From 'Conversations with a Stoner'

Not far from Assisi, home of the man so conceited he thought the birds had something to learn from him, there lies Gubbio, where good old Francesco thought he'd have a crack at wolves too. There's any number of churches and the like there, but more interestingly, if you walk a short way up the gorge behind the town you can see an exposed section that clearly shows the location of the Cretaceous-Tertiary (K-T) boundary.

The K-T boundary is the fancy name for the boundary between the rocks where we see dinosaur fossils and those where we don't. The K stands for Kreidezeit, which is the name (meaning "chalk time") the Germans give to what we call the Cretaceous, the time after the Jurassic. (The Jurassic, made famous by the Spielberg film, gets its name from the Jura mountains in Switzerland, where we started our trip. The dinosaur used in the "Jurassic Park" logo is actually a Cretaceous dinosaur, but they thought it looked cool.) During the creatureful Cretaceous, there were dinosaurs (and the chalk of their bones). By the Tertiary, there were none.

(The picture is looking down towards the town from the gorge, so if you're using this page as a guide, turn back now! You're going the wrong way!)

Here you see one of the furry little mammals who so profited from the dinosaurs' relegation to the creatures that San Francesco thought he could teach a thing or two. His foot's on the layer of light-coloured junk that marks the boundary. To the right, there be dragons. To the left, there be things with hair & breasts.

It was this white stuff (the rock, not the monkey) where those geeks found the unusually large amounts of Iridium, something you'd more usually expect to find in a meteorite, and made the "meteorite impact killed the dinosaurs" thing so trendy. Not everyone believes in this, though, and I'm not just talking about Christian fundamentalists and their ilk. Bob Bakker, the dude who made the "dinosaurs were warm-blooded" theory cool, isn't convinced. See his book "The Dinosaur Heresies" if you're interested.

And here's my duffel-coated co-conspiritor. He's looking so happy because we moved the signs 100m along the road, and I bet there aren't many of you capable of knowing whether you're looking at the real thing or not, are there? It's an interesting question that everyone asked when they heard how I was spending my holiday: Why? What's the point? And the answer is, of course, that there isn't any point. I don't know any better than you that those were really the rocks, and if I don't know, how can it be important?

Maybe it's our monkey heritage: maybe a thing isn't really real for us if we can't see it. Why else would we go to art galleries to be disappointed by the fact that "It's smaller in real life, isn't it?", or stand in a crowded square waiting for the Pope when we could see him in (barely) living colour on TV at home? It doesn't make sense, but it's kind of cool anyway, and there's nothing better to do, so why not?

The black bag in the foreground, by the way, contains as much of this site of international scientific interest as we thought we could carry.