Slightly bigger than a 35mm film canister.
We spotted this culvert, behind the caution sign, and thought that it would make an interesting stop.
Have you ever noticed or considered these culverts on our roads? They are very important to ensure proper drainage so that our roads don't deteriorate. Sometimes it seems that they culvert is not doing its job correctly, as our roads are in a sad state of affairs. Fortunately, on this road they seem to be doing their job well.
According to Wikipedia, a Culvert is a device used to channel water. It may be used to allow water to pass underneath a road, railway, or embankment. Culverts can be made of many different materials; steel, polyvinyl chloride (PVC) and concrete are the most common. In the past, culverts were commonly constructed of stone.
Acknowledgements: en.wikipedia.org/wiki/Culvert