I'll talk a bit about the telescope and my own visit, with a few photos, below the jump.
The actual receivers are in a three-storey-high dome that serves to focus the incoming rays back to a point after being reflected from the spherical main dish. This dome moves back and forth on a rotating azimuth arm so that the telescope can see about a forty-degree circle of sky. Over the course of a day, this lets the telescope see a band stretching from about declination zero to about forty degrees. To get out to the dome, you climb down a ladder inside the azimuth bearing, then hop out through some girders onto the arm. It looks like there are some arm positions where you can't really get from one to the other, and, more disturbingly, there's no safety interlock — it's up to you to make sure you're not in it when the telescope moves. Granted, it doesn't move that fast — maybe five minutes to turn 180 degrees? — but the arm is so massive it wouldn't even notice if you were in the way. The jump from the arm to the dome is much less alarming, just a step from a walkway to a platform on the dome. Inside the dome you can enter the receiver room, where there is a large turret that can rotate the various receivers into the focus. I was amused to note that the receiver I usually use — the L-band wide — is literally held together with duct tape and bungee cords. Works well, though.
Altogether the telescope is an amazing machine. The physical structure hasn't changed all that much, apart from a resurfacing, but the electronics are constantly being improved; for example there is now a multi-beam receiver that gives you seven whole pixels at a time! There are things you need another telescope for, but when you need the highest possible sensitivity, there's nothing that can replace Arecibo. Unfortunately, its funding is under significant threat right now. Let's hope we can save it.