Cannon's Marsh Gas Works

Tim Bray took a stroll on the Bristol Harbourside and found a mystery building.

Our river’s-edge meander pretty quickly took us off the beaten track, I’m not sure what these are the ruins of. […]

It’s the ruins of Cannon’s Marsh Gas Works, apparently they used to produce the gas from whale oil. Toponymical factoid: the road opposite (on the other side of the harbour) is called Gasferry Road.