The Blackfriars Antiviaduct
A mysterious sight in London can be found next to Blackfriars Bridge. It's a set of what look like bridge piers running alongside the railway bridge (picture).
It's often assumed that these are the remains of an older bridge that was removed when it became obsolete. Not so. It is in fact that still very much operational Blackfriars Antiviaduct, a thrilling piece of Victorian innovation in the built environment.
An Antiviaduct is, in effect, an upside-down bridge - the vehicle-way runs along the river bed and the piers stick out above the water. Feeding into the Blackfriars Tunnel System (as previously explained on TiL), it was part of a route for the submersible Hackney ferries that crossed the river in the early part of the century after the invention of the Horse diving suit. These submersible Hackney carriages were a vital means of alleviating cross-river traffic as the surface ferry routes and bridges choked up; although hard work for the horses, they were a huge boon to their users.
But why, you might ask, would a bridge along the riverbed need piears at all? In fact, that's a foolish question as we are talking about a time when the suspension bridge was white-hot technology and still not in widespread use, so obviously the bridge needed piers to stop it floating to the surface. It would be years before a single-span Antiviaduct would be possible, and by then technology had moved on and the horse-drawn submersible Hackney Carriages were no longer needed.
A tourist service still operates at weekends during the summer holidays (low tide only).