Conversation so far:
What did Ludwig Mies van der Rohe do first in his career?
Ludwig Mies van der Rohe worked in his father's stone carving shop and at several local design firms.
What design firms did Ludwig Mies van der Rohe work for?
Ludwig Mies van der Rohe joined the office of interior designer Bruno Paul.
What did Ludwig Mies van der Rohe create there?

Question: What was his biggest project?
Self-contained rewrite: What was Ludwig Mies van der Rohe's biggest project?