I mean the ones shown in this map https://www.metropolitan.bg/assets/resourceimages/908/3D-%D0%9D%D0%94%D0%9A.jpg on either side of the fountain with the metal balls towards platform B. On OSM, there's only one access path (where the note is) that branches off from the underground passage in front of NDK right in the fountain. I plan to survey this myself next week