This was a ground-breaking game for its time, and was the first adventure game ever made for a gaming console. Although incredibly primitive by today's standards, it becomes incredibly impressive when you realize that the Atari 2600 only had 4K of ROM and 128 bytes of RAM. Warren's home page has a page devoted to Adventure. In it is a PowerPoint presentation about the making of Adventure, including a quick summary of the Atari 2600's architecture. It is a great read if you're into legacy hardware/software platforms and the programming techniques needed to develop code for those platforms.
Interestingly, back in the 70's, when Adventure came out, my father and I found the Easter egg, learning all about Warren Robinett. We phoned Atari, hoping to be able to talk with him for a few minutes, but the receptionist claimed that no such person ever worked there. At the time, we assumed that he had been fired for wasting memory with the Easter-egg room which could have held another game room. In hindsight, I think it is more likely that we weren't the first to phone up, and Atari was trying to make the callers go away so their engineers could get back to work.