These undergrounds are all over Kyiv, safe paths across underneath roads. They are generally filled with pedestrians and salesman during the day... at night, they strike me as perfect crime spots.... hmmmm, oh well! Been lucky all these years, but also, a trick applies to every major city in the world.
"Eyes looking forward and behind", its not impossible. Apparently its a feature built-in City folks, Habana, NY, Kyiv, London. Yup! City fun.