This is all the data I am aware of (but some of this* may be open for interpretation):
- Overall size of the building: 7,000m² (or 0.7 hectares / 70 acres)
- *Combined floor size of the elephant area: a bit more than 3,500 m² (this is what the internal documents for the companies stated in the written text so this should be accurate)
- but effective "walking area" rather "close to 3,000 m²" (the given measures in the attached plans for said companies actually add up to something up from 2,700m²), possibly with some additional spaces reachable by the elephants' trunks (safety zone of the pool, holes/small caves in the enrichment structures) but also some "dead" areas like plant zones, structring rocks or possibly even walls
- The transparent roof alone covers 3,500m² but it probably covers some none-elephant-zones while it likely wouldn't cover some of the elephant area behind the scenes as far as I (so I am not sure, how helpful it really is as a rough orientation).
- The three outside areas make up 4.835, 4.033 and 3.538 m² respectively.
So you can assume, there at least up from 2,700m² (0,27 hectares/ 27 acres) and at most up from 3,500 m² indoor area and just slightly above 12,400 m² outside area. The claim "biggest elephant house" of Europe may refer to the entire 7,000 m² as the building is now mainly designated to the elephants and the needed structures/ infrastructure, whereas other animals and visitors only receive small chunks by comparison.
You may get a bit of a better idea, if you enlarge the picture in this older press release:
Gut Ding will Weile haben – Zoo Berlin (tierpark-berlin.de):
Image: Tierpark Berlin
And you can also get some aerial views, if you enter "Dickhäuterhaus Berlin" or "Tierpark Berlin" (without the problem with the "Umlaut") on this page:
Dickhäuterhaus Berlin - Luftaufnahmen (luftbildsuche.de)
There are actually some interesting updates with snow from last November which might help get a good impression.
To cut a long story short, the elephants will get plenty of inside and outside space as well as plenty of structures for enrichment and medical treatment etc without any direct contact. It's another question, if it really fulfils the double claim "largest elephant house in Europe" and "most modern elephant house in Europe". However, it most certainly will be among the best, largest (and most expensive) elephant buildings in Europe...