You can do it with the editor, by turning debug mode on. This'll work for conquests, I'm not sure about versions before that. Let's see, the procedure would be:
1) Start up editor, go to Scenario->Scenario Properties, check Debug Mode, hit OK.
2) If you want to watch but not play, you need to put your own civ someplace out of the way. Skip this step if you want to play. Choose map->generate map and choose how you want the map. Find or make an island in the middle of nowhere. Do Map->Set Active Player->Player 1, then do Map->Select Brush Type-> Overlay->Player Starting Location and put it on the island.
3) Then Save As, call it something like "observe" and put it in the Conquests\Scenarios folder.
4) Start up conquests, choose Civ Content and then pick "observe.biq" or whatever you called it. That should do it. Now, watch how utterly idiodic the AI really is!