There are several experiments going on at CERN, but the big one, the one everyone’s excited about, is the LHC. It’s still being built, but when it’s done it will be by far the largest accelerator ever made. We’re talking an order of magnitude more powerful than the runner-up, the Tevatron at Fermilab (just outside of Chicago).

But what is a collider? I’m so glad you asked. A collider is a big ring (actually a pair of rings, one right inside the other). Its job is to accelerate particles (in this case protons) in both directions. It gets them up to
very close to the speed of light (about 99.9999997% of the speed of light) and then smashes them together in a head-on collision. This isn’t very healthy for the proton (the parts of it that aren’t annihilated instantly are shredded into several hundred pieces) but it turns out it’s a pretty good way to find new physics. We build huge detectors at the points on the ring where we’re colliding the particles and see what comes out.
Physically, the LHC is an enormous underground ring 27 km in circumference, which comes to about 5.3 miles in diameter. Seriously. It's 5.3 miles in diameter. That’s the distance from Townview to the Café Brazil on Central, and it’s all one giant machine. You could fit several small villages on the inside of this thing. And I know, because when I drive out to Point 5 on the circumference of the ring, I have to go through several small villages. So the thing is pretty big.