The latest missive from the Cambridge Astronomical Association arrived this morning. In the current edition of Capella, their newsletter, is a fascinating article about how the sky brightness varies with altitude. The naked eye limiting magnitude was a whole magnitude fainter at 120m above street level! The observations were made from a 35th-level apartment and from the street immediately below in a Bortle 7 and Bortle 8 sky respectively.
https://www.cambridgeastronomicalassociation.com/ for more about the CAA and access to their newsletters.