Newgate

Newgate was one of the historic seven gates of the London Wall around the City of London and one of the six which date back to Roman times. From it, a Roman road led west to Silchester, Hampshire Excavations in 1875, 1903 and 1909 revealed the Roman structure and showed that it consisted of a double roadway between two square flanking guardroom towers.

From the 12th century, at least, the gate was used as a prison for debtors and felons. This, the notorious Newgate Prison, was later extended to the south on the site of the modern Central Criminal Court on Old Bailey. The gate was demolished in 1767.

More information on the Wikipedia page.