The starlings on Tower Bridge can be clearly seen beneath the roadway.

In architecture, a starling (or sterling) is a defensive bulwark, usually built with pilings or bricks, surrounding the supports (or piers) of a bridge or similar construction. Starlings are shaped to ease the flow of the water around the bridge, reducing the damage caused by erosion or collisions with flood-borne debris, and may also form an important part of the structure of the bridge, spreading the weight of the piers.

One problem caused by the use of a starling is the build up of river debris, mud and other foreign objects against the starlings, potentially blocking the flow of the river.