30,000 was quite high enough for me, thank you. You need pressure breathing above that.
I once took off from Oakington at around midnight on a beautiful moonlit night. Controlled Airspace stopped at about 27,000 ft. in those days so I climbed up to 30 and orbited over central London. You could see Birmingham one way and over the darkness of the Channel I think I saw the lights of Paris.
Later on in life we did the last radar bombing run before the bombing task was removed from our tanker squadron. The target was King's Cross station which was one of the radar targets. Again a beautiful moonlit night and at 40 you could see a lot more.