Completed in 1209 under the direction of Peter of Colechurch, Old London Bridge was an unprecedented marvel of medieval civil engineering. Spanning the volatile tidal waters of the River Thames, it was far more than a crossing point; it was a thriving, congested urban neighborhood suspended over water. To support the immense weight of up to 200 multi-story wooden buildings, medieval builders relied on nineteen stone arches anchored to massive timber-encased artificial islands called starlings.
These starlings were constructed by driving concentric rings of oak piles deep into the riverbed, filling the interior with rubble, chalk, and stone. On top of these solid piers, builders erected timber-framed structures up to seven stories high. To prevent the heavy structures from collapsing into the river, houses were built with cantilevered upper floors that leaned outward over the water, connected by overhead wooden arches called braces that crossed the narrow road to act as structural struts against opposing buildings.
The weight of the buildings actually served an engineering purpose by stabilizing the stone piers under vertical compression. However, this dense living arrangement created a hazardous environment. The narrow central street was barely six feet wide in places, blocking sunlight and creating a wind tunnel for fires.
Below, the bulky starlings restricted water flow by up to seventy percent, turning the Thames into roaring rapids known as shooting the bridge. Despite fires, floods, and ice, this suspended city endured for over five centuries.