A city is where sirens make white streaks of sound in the sky and foghorns speak in dark grays. San Francisco is such a city...
We know that Bryon took words off of buildings (in Verse 12 with M and B) and monuments (in Verse 4 with Socrates, Pindar, Apelles) to weave into the riddles of his verses. JJP corroborated that when he said: "Byron was notorious for doing that... he picked those words off that building".
With that in mind, let's take a look at a couple of lines from Verse 7:
Sounds from the sky Near ace is high
At 445 Bush St, about 200 ft from the Dragon's Gate, we have the Pacific States Building, built in 1905.
The Japanese hint for "Sounds from the sky" tell us to think about the kinds of sounds that "can only be heard using specialized equipment/machinery". There are a few plausible interpretations, one of which is the telephone. The sounds of people's voices travel through the sky on telephone lines and a telephone is the specialized equipment for hearing those sounds.
Sounds from the Sky = Pacific Telephone and Telegraph Company
Directly across the street, at 460 Bush St, we have the SFFD Engine Co. No. 2, built in 1908. Looking up at the building, you'll see a very prominent 2. If the "ace" in "near ace is high" is referring to a playing card, then it's describing the first card in the deck. The card nearest to the ace is the deuce (2). We can reframe that line, with simple substitution, as "deuce is high". (shout out to forest_blight for getting me thinking in this direction)
Near ace is high = SFFD Engine Co. No. 2
What a clever way to pick words off buildings...