THE OLD WATER GATE.
In a corner of the public gardens on the Victoria Embankment, at the foot of Buckingham Street, is the ancient Water Gate to York House, a mansion begun by Inigo Jones for the first Duke of Buckingham. It is a beautiful monument of the famous architect's skill, and can challenge comparison with similar work by any of the Italian masters. This old Water Gate is the earliest ornamental archway in London. It is interesting, moreover, as showing the former level of the Thames. This part of town was a very different place once, when the nobles fancied it for their mansions, or even prior to the making of the Embankment, when it was regularly, lapped by the tide.
source: The Queen's London : a Pictorial and Descriptive Record of the Streets, Buildings, Parks and Scenery of the Great Metropolis, 1896