User blog comment:Hdutt2/Hdutt2's BioShock: Downfall-Novel: Prologue and Note by the Author/@comment-6024608-20131006075620

" he built Rapture, the city under the sea. With technology thousands of years ahead of its time this city grew to become a wonder. "

Actually the technology already existed in the 40's useable within reasonable depths like 600-1000 feet (assumes that 6 mile deep stuff is just crazy Splicer mumblings - as there are no near 6 mile deep spots in the Atlantic anywhere near Raptures location).

Some of the technology was advanced (alot wasstill  vinatge 40s/50s)  but little is  star trek like which itself is only a few hundred years in the future.

---

Now all those other 'Cities' can be completely different timelines and tech levels ('infinite' opens it up to just about anything --- an underwater city of Atlantis-like pseudo-phoenicians  3500 years ago...)