http://www.buzludzha-monument.com , https://en.wikipedia.org/wiki/Buzludzha ,
https://www.atlasobscura.com/places/buzludzha-monument ,
https://www.nationalgeographic.com/travel/destinations/europe/bulgaria/things-to-do-buzludzha-monument
https://www.google.com/maps/place/Buzludzha+monument/@42.7355022,25.3921853,3337m/data=!3m1!1e3!4m13!1m7!3m6!1s0x40a8fe29f7f408a7:0x7030468d64a55d2d!2sKhadzhi+Dimitur!3b1!8m2!3d42.7333333!4d25.4!3m4!1s0x40a901d1178b3a53:0x90c9aa019c113773!8m2!3d42.7360272!4d25.3936636!5m1!1e4