The location is approximate since no geographic information was attached to the picture, but it is known that it was taken near this place.
Thanks to Vuori Susi for deciphering the text and its meaning ТАЛВЕГ - TALVEG - The manhole builder Т.Т.КАБЕЛИ - t(elephone and) t(elegraph) cables. БДС (Българският държавен стандарт) - Bulgarian State Standard