Some ideas feel as though they've been around for a long time. Like putting the two enemy bases back to back. And with some ideas, it's that extra twist that makes it work, like having a glass wall between the two.
SirTahngarth has just released a map that does just this: Spyglass. The entire map is divided by a huge glass sheet. (I have a feeling it's a remake of something he did for UT Jailbreak, but that much glass surely wouldn't have worked back then.)
For those interested in history, a development old screenshot was our pic of the week, many moons ago. But if you just want to download and play it, I have a word of warning: look out for falling mines!