The Babel Project

The Babel Project is arguably the greatest undertaking in the Seraph of the End series. Sika Madu was involved in the Babel Project in a campaign to return seraphs to paradise. Featuring technological aspects, it was more ambitious and made use of advancements that were never seen to have been developed by modern times.

Background
During Earth's prehistory when dinosaurs were alive as the dominant species on the planet, long before humans had even evolved, Earth was designated by an organization of some kind as the Sol System First Satellite Kingdom. The Babel Project may have just referred to the operations on Earth, or across at least seven astronomical objects where colossal structures were being built. It is probable that both seraphs and homunculi were involved with the Babel Project.

Features
The Tower of Babel was one such creation which shares its name with the titular project. Technology based features involved included Unrailed Elevator Technology. It is likely that the Photons, the source of seraphs' power were also used in some capacity.

Story
When Yu and Mika have delved into memories they come across Mikaela who was seen to be alive in the prehistoric past. Following him to a seraph civilization, they enter the by far tallest building in the civilization, namely the Tower of Babel. Within the inner wall around the tower, an announcement welcomes denizens to the Babel Project.

"Welcome to the Babel Project. The purpose of this project is to return us to paradise. By making use of unrailed elevator technology, we will..."

- An announcement to seraphs and homunculi

Details of its purpose and what is involved with the Babel Project are mentioned upfront. What the unrailed elevator technology could help the seraphs with is hot heard by Yu and Mika however as they took their limited chance to head further into the tower.