divide the map into two - three peices (AKA levels)
this also means older parts of the level may not be accessable unless recreated and coordinated with definate changes. like you cant have something explodable in the re-acurring part because if they blow it up it would suddenly be there again and break any kind of reality that you might have built up. The game in general can sustain only so many poly's at once so it could be divided up but still run slow in some sections because of map conflict and or high poly count. you may just have to face the facts of either long non detailed maps or very short detailed maps. I suggest you vary them to give more depth. owe by the way use doors and walls to to block player views this helps reduce the amount of rendering. use the "[" and "]" during test play to see wire frame this would help.
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