Lidar will ultimately allow us to map archaeology everywhere, not least in the Mississippi Valley and the Amazon where populations in the millions once existed. Here we get a taste of its efficiency as the full extent of the Khmer empire emerges.
It also shows us that true multi generational empires do fall apart, likely through barbarian invasions that eliminates the state's security apparatus. That allows marauders to loot and drive populations into the jungle
That is what happened to the bulk of the Roman world and what survived was the Church and that barely. Obviously that was the exception. We have many extinct antique empires for which we know nothing and dearly wish otherwise.