The cupola of the Bank of England is the small dome structure surmounting part of the Bank’s building, most notably at the Tivoli Corner—the north-west corner designed by Sir Herbert Baker during the 1920s-30s reconstruction.
This cupola is a distinctive architectural feature that sits above a passage at Tivoli Corner, inspired by the ancient Temple of Vesta at Tivoli. Atop the cupola stands a gilded bronze statue named Ariel (after the spirit in Shakespeare’s The Tempest), giving the corner a unique visual identity. The dome and its statue are recent compared to other parts of the building, as most of John Soane’s original Bank (late 18th to early 19th century) was demolished in the interwar redevelopment, with the perimeter wall and certain features (like Tivoli Corner) preserved or reimagined by Baker.
 
Interesting fact...
The demolition of Sloane's original building is considered the greatest act of vandalism in the U.K. A loss of one of its greatest buildings.