At which venue did Zeppelin achieve the largest attendance record for one act on one night?

Answer 1

Pontiac Silverdome, Michigan, U.S.A..

An amazing 76,962 were in attendance on the night of 30th April 1977.
The tickets for the concert sold out in less than 1 day, with gross receipts for 792,361.50 dollars. These figures have of course been broken many times since by the likes of 'The Who' and the 'Rolling Stones'. A reunion tour would I'm sure restore the record back to Led Zeppelin without much problem.