That's because there is a birthday celebration hall with two towers, which belong to Zen master Haiyun and his disciples respectively. Zen master Haiyun was a famous monk in the late Jin Dynasty and early Yuan Dynasty. He is a religious leader authorized by the Mongolian emperor and is regarded as a "national teacher". His apprentice is Liu, the chief designer of Yuan Dadu.
When the Yuan Dynasty was first built. The location where the Twin Towers pass by the South Wall, but out of respect for the Zen master Haiyun, Kublai Khan let the wall bypass the Twin Towers to the south and circle into the city, so the South Wall of Beijing is very conspicuous.
Later, when Chang 'an Avenue was built in the 1950s, the Twin Towers were destroyed.
Again, that conspicuous position is not on the wall of the Forbidden City, nor on the wall of the inner city of Beijing or the imperial city of Ming and Qing Dynasties, but on the wall of the Yuan Dynasty, and the specific position is near the telegraph building on Chang 'an Street.