Los Angeles Arcology
Though construction of the massive structure had been proceeding for 10 years, the incredible size of the monolith meant that there would be many more years of construction to go. However, a sudden invasion of the Esoteric Order of Dagon on the shores of Santa Monica and Malibu Beach brought ruin to many rich and important people. Their sudden interest in seeing the arcology finished meant that the project was rushed.
In effect, the arcology was finished in a record 17 years due to an unheard of construction force. The sudden rush also meant many more slip ups and frequent miscommunications between the many contractors. As a result, there are said to be many buildings, streets, maintenance structures, even entire neighborhoods lost within the arcology.