The monument at a depth of 7 meters is the "chillakhana" of Mazlumkhon-Sulu

It is one of the unique monuments in Central Asia, located in the above-mentioned site of the ancient
settlement Mizdahkan. 

In fact, the multi-cell structure was set in the ground in the depth of about seven meters, and only its dome is above the earth surface. Experts age-date the monument as not later than the end of the 13th century AD. 
 

Due to the specific construction and the set-up of the monument in the crypt, the tradition can be related to the arrangement of Sufi subterranean shrines (chillakhana); that the custom dates back to the traditions of the Yassawiya Order. 

According to the legend, Khoja Ahmad Yassawi (died 1166), having reached the age of 63 per Islamic (Lunar) calendar, declared to his followers that he did not wish to see the daylight longer than it had been done by the Prophet himself, and voluntarily retired from the worldly life to the hypogeum where he spent a long time in contemplation and devotional rites (zikr).
 

In case there are enough reasons for such a comparison, then Mazlumkhan-Sulu who was buried here might have also adhered to that tradition. Following his death, his worshippers probably constructed a hall to carry out the rites (khanaka) and a burial place in his subterranean abode. To preserve the aforementioned tradition, the construction of the monument in the crypt may have followed that same custom of subterranean abodes.