Archaeologists excavating residences in the ancient Nubian city of Old Dongola in Sudan made an unexpected discovery: a complex of rooms hidden beneath the floor.

Researchers leading the excavation found the rooms' walls decorated with Christian paintings dated to the Funj Period (16th-19th centuries C.E.), according to a press release from the Polish Centre of Mediterranean Archaeology at the University of Warsaw.

"Seems that [the] gods of excavations favored us in the very last season of [the European Research Council’s] UMMA grant," archaeologist Artur Obluski wrote in a Twitter post, referring to the "Urban Metamorphosis of the community of a Medieval African capital city" (UMMA) grant that authorized the excavation of Old Dongola, known as Tungul in pre-Nubian times.

A Nubian king bowing to Christ as he receives a blessing is featured in one of the paintings, with Archangel Michael's wings spread to protect both the king and Christ.

Another painting shows Virgin Mary in an unusual style, having a book and a cross in her hands and wearing a dark robe.

"These wall paintings negate a bias that Africans tried to awkwardly copy art from the North," Obluski commented on the painting's motifs in another post, adding that "They were creative, adapting, not only adopting, world trends to their needs, thus the new paradigm should be Nubio- and Afrocentric."

The paintings and the rooms are unique and mysterious; the space was oddly shaped and quite small. It is elevated above ground level, so researchers believe it was unlikely a tomb.

They proposed that the paintings were made in this secret space as King David and his army of slave soldiers approached Dongola.

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