Bluebulb Projects' The Measure of Things presents:
91,000 is about two-and-a-half times the number of Seats in Fenway Park.
In other words, it's 2.45470 times the count of Seats in Fenway Park, and the count of Seats in Fenway Park is 0.407380 times that amount.
(2013 figures; daytime capacity) (a.k.a. The Cathedral of Boston) (Boston, Massachusetts)