The expedition first identified the monumental structure in 2021.
Excavations became possible after the team received a grant from Poland's National Science Centre. The work is led by Prof. Artur Obłuski, director of the University of Warsaw's Centre of Mediterranean Archaeology.
Obłuski said the Great Church of Jesus may have been a building that set architectural trends in Nubia and possibly in this part of Africa, much as Hagia Sophia in Constantinople did in its region. Such buildings influenced both spatial planning and technical solutions.
Only a small section of the Great Church of Jesus has been excavated so far.
Researchers have established that it was 47 metres wide and about 57 metres long, while its height is cautiously estimated at 21 metres.
Obłuski said the building was larger than the White House in Washington and that the team planned to excavate it. This will require particularly deep excavations and greater resources than usual.
Researchers were also surprised to discover another church in a building adjoining the Great Church of Jesus. It was located on an upper floor of a structure added to the main church. Its walls survive to a height of only about one metre, but archaeologists found traces of painted decoration.
The team also found painted decorations in the Great Church of Jesus and small fragments of plaster bearing Greek inscriptions in the fill of the smaller church.
Agata Deptuła, the expedition's epigrapher, said these were fragments of biblical canticles or odes, religious songs added to the Psalter.
The excavation season was preceded by work to protect the site, carried out with the Warsaw University of Technology's Faculty of Civil Engineering.
Obłuski said Old Dongola had been damaged by the largest flood since 1988 in autumn 2024, which also damaged some roofs protecting archaeological remains.
The expedition also installed a photovoltaic system funded by the Polish foreign ministry's Polish Aid programme. It is intended to support the archaeological site by supplying electricity for pumps bringing Nile water to the homes of around 10,000 people and for irrigating their fields.
(sp)
Source: PAP