Another restoration (details unknown) took place under Abdul Hamid II (r. 1876-1909) (Basilica Cistern, Istanbul Heritage, https://www.basilicacistern.gen.tr/history/).

Forchheimer and Strzygowski, 1893, p. 55 shed more light on the situation at the end of the 19th century. The cistern stairs used to be accessed through a trapdoor opening measuring 95 × 65 cm in the floor of a house at the Şeftali Sk. (according to Forchheimer and Strzygowski belonging to a merchant from Adrianople/Edirne). Apparently the cistern was flooded with water, and without a boat that fit through the opening of the trapdoor, it could only be explored to a limited extent; for the unexplorable parts, the authors relied on Gylles/Gyllius, who explored the cistern with a boat in the 16th century. The authors also report that the cistern was still in use in the 19th century; they reported that the water was not used for drinking as according to Gylles, large fish lived in there.