This is an apsidal niche with a coffered ceiling decorated with classical mythological and ornamental panel paintings, designed by the original architect Friedrich August Stüler.
It survived the heavy Allied bombing of Berlin during World War II, though it was left heavily damaged and exposed to the elements for decades.
When British architect David Chipperfield and restoration specialist Julian Harrap reconstructed the Neues Museum between 2003 and 2009, they chose not to replace or repaint these damaged areas.
Instead, they meticulously conserved the original, surviving 19th-century dome vault structure and its peeling frescoes to serve as a visible record of the museum's layered history and survival.
There is usually an artifact sitting inside this specific glass vitrine for display, but during that moment of my visit, probably that piece was removed for rotation.