The view out of Mrs. Wentworth's and Harry Down's apartment windows are the same - the Subway Terminal Building at 417 South Hill Street in Los Angeles - even though their apartments are across the hall from each other.
When Mike goes out on the ledge to chase after Kitty and Johnny, Kitty slips and Johnny grabs her while holding on to the window frames beside him, causing them to bow out and revealing there is no glass in that window.