It's a bit of a misconception to say Einstein "discovered" E=mc². He derived it as a consequence of his theory of special relativity, which he published in 1905.

So, while the famous equation wasn't discovered in a specific place, it was a product of Einstein's theoretical work, likely developed in his office or home, as he was a theoretical physicist.

Here's a breakdown:

* 1905: Einstein published his paper "On the Electrodynamics of Moving Bodies," which laid out the foundations of special relativity.

* Within the same paper: He derived the equation E=mc² as a consequence of his theory. It's a direct result of the principles of special relativity, particularly the equivalence of mass and energy.

Therefore, while Einstein didn't "discover" the equation in a physical location, it was a direct result of his groundbreaking work in theoretical physics.