Complex sentence: Many small pockets of civilization exits; from isolated super high-tech fortresses, hidden research labs, or racial groups in walled-in cities, fighting each other, amongst the more regular population, which in many ways resembles the "old west".
Split into simpler sentences: Many small pockets of civilization still exist; from isolated super high-tech fortresses, hidden research labs, or racial groups in walled-in cities. All fighting each other among the more regular population which in many ways resembles the "old west".