The British Library building with a dome 45 metres in diameter, built in the 1850s

The British Library building with a dome 45 metres in diameter, built in the 1850s. Or, to be precise, the circular Reading Room of the British Museum, with iron bookshelves running round its perimeter.

The total length of the Reading Room's shelving is 25 kilometres. A considerable area is taken up by skylights, for the building went up in the days before electric lighting. The room was designed for 302 readers, who were accommodated at 38 desks radiating like spokes from a keyhole-shaped catalogue at the centre.

The British Library formally separated from the British Museum in 1973, but continued to occupy the domed building inside the museum until 1997, when a separate complex was built for it elsewhere. The Reading Room itself underwent substantial reconstruction and was given over to the museum's archive, with its architecture and historic interiors preserved.