The Black Chamber is the best-preserved monument of Bulgar architecture. It is one of the most beautiful and mysterious structures of Bolgar, built in the 14th century from white limestone. The Black Chamber got its name either from the very status of the building, where "black" (serious) cases were examined, or after the fire of 1361, when the building was completely burned down.

Archaeologists and historians debate the purpose of the Black Chamber. Some believe that the upper level housed the Khan's court, and the basement was a prison. The court was conducted by the Khan and a council of three people. When it was necessary to hold court, the Khan and each of the judges entered the chamber through special doors corresponding to the cardinal directions. The Khan always entered through the western doors.

Others think that this was a mosque of the craftsmen’s town. In the 14th century, Bolgar was at its peak, attracting many craftsmen. The settlement where they lived was located around the Black Chamber. A third theory suggests that the Black Chamber was most likely a khanaka with cells for wandering dervishes. Scholars, relying on excavation data and documents, concluded that it is a purely secular building. Remains of a water supply system were found, which is incompatible with either a religious building or a burial site.

The Black Chamber in a painting by artist A. Savrasov

The Black Chamber had annexes and a surrounding gallery with stairs that allowed access to the second floor. Unfortunately, the gallery has not survived. Excavations in recent years have established that the Black Chamber is one of the rooms of an entire architectural complex. Archaeologists found the foundations of seven buildings around it.

Poetic legends explaining its name have been preserved. "During the sack of the city of Bolgar by Aksak-Timur, Khan Abdullah, with his family and close associates, took refuge in this building. The conquerors, by order of the formidable emir, surrounded the building with wood and set it on fire. Everyone was supposed to perish in the fire and smoke, but when the smoke cleared, the enemies saw a girl in white clothing on the roof of the building. This was the Khan’s daughter. Aksak-Timur, amazed by her courage and beauty, offered her to become his wife. She refused. Then the enraged emir ordered her two brothers, sentenced to death, to be brought to him. Seeing her brothers with shackles around their necks, she paled and shouted to the conqueror that she agreed to become his wife if he released her brothers in her presence and gave them the best horses. Thus, she saved her brothers’ lives, and she herself threw herself onto the burning logs and died. The building remained blackened from the fire."

Another legend says: "In the second half of the 14th century, a feud began between Tamerlane and the khans of various uluses of the Golden Horde. Because of this, Tamerlane undertook several campaigns into the Volga lands. During one of them, he captured Bolgar. According to legend, Tamerlane wanted to execute the khan, but he and his family took refuge in the Black Chamber. Tamerlane ordered the building to be surrounded by logs and set on fire. After the fire, on the roof of the Black Chamber, Tamerlane and his warriors saw a girl in white clothes. This was Princess Gaysha-bike. She was famous for her beauty and holiness, so Allah saved her."

Or perhaps it was much more prosaic: later, in the 19th century, monks from a nearby monastery arranged a smokehouse in this building, which is why both outside and inside the building actually turned black.

The Black Chamber has a quadrangular cubic base, transitioning into an octagon, then a hemispherical dome. The upper part is built of light tuff, the lower part of limestone. The cubic part is divided into three tiers: the first tier has an entrance on the northern side; the lower tier is separated from the upper by a floor, for which there is a ledge. Doors from the east, north, and west led into the second tier. On the southern side, there was a niche. The entrance and niche are crowned with pointed arches; traces of plaster and decorative finishes in the form of rosettes, half-columns, and cells remain on the inner wall surfaces.

There was a sharp contrast in the room’s decoration. The tall, light, domed hall with once rich stucco decoration was opposed by the gloomy, windowless rooms of the first floor. The purpose and use of this building are disputed. Some scholars believe this building was a courthouse, linking it to local legend: the first floor of the building is more suitable for temporary detention of the convicted.

Others consider the building a mosque or madrasa; a third group suggests that the Black Chamber was most likely a khanaka with cells for wandering dervishes. Khanakas appeared in Eastern countries in the early Middle Ages. They served as gathering places and shelters for wandering dervishes. In terms of layout, khanakas consisted of a main room—a spacious prayer hall—around which were living cells for pilgrims. Usually, the prayer hall had four entrances symbolizing the four schools of Islam (Evpatoria Khanaka).

The Black Chamber had annexes and a surrounding gallery with stairs that allowed access to the second floor. Excavations in recent years have established that the Black Chamber is one of the rooms of an entire architectural complex. Archaeologists found the foundations of seven buildings around it.

Thanks to the preservation of the Black Chamber, in the 1870s the Society of Archaeology, History, and Ethnography at Kazan University established a museum of antiquities here. Tombstones, reservoirs, large architectural details, and more were collected here.

From 1884 to 1926, the Black Chamber was restored with red brick. In 1956, the dome of the building was restored. In 1976, restoration of the monument began, followed by continued restoration of the walls. Openings blocked by later additions were uncovered. In 1987, the restoration of the monument was completed. Restorers created the interior of the Black Chamber, primarily cleaning the walls from later layers, whitewashing all the interior wall and dome surfaces, restoring architectural stucco details of the interior, laying a wooden floor over the basement tier, and installing a staircase connecting the levels of both tiers.

Sources:

https://ru.wikipedia.org/wiki/Болгар

https://yanarysh.tatarstan.ru/blackchamber.htm

https://appreal.org/tatarstan-64-object/