There is a forest there right now.
The video provided by J.-U. Koehler proves that Tesla will have to clear some forest near the Freienbrink industrial area. Other than that, the entire infrastructure, including railway, is probably on hand.
Tesla is expected to start the construction in 2020 as the Tesla Model Y production is scheduled for 2021.
Tesla intends to produce battery packs and powertrains on hand too. According to the latest unofficial reports, based on Tesla's job advertisements, the production of lithium-ion cells also might be part of the plan.
"Teslamag has formulated this assumption, basing it on job advertisements for Gigafactory 4, where, among other things, it can be read that applicants should be able to create “innovative detailed designs for a wide range of systems from electrolytes to high-purity water”."
Tesla Gigafactory 4 at brief:
- to be located in the Berlin-area, Germany, (near the new airport)
- to produce Model 3/Y starting in 2021 with the Model Y
- will produce also batteries (for sure modules/packs) and powertrains