Along the road

Something different for a change, even though I could choose from close-ups of forget-me-nots, Japanese quince and other garden treasures from the garden in Holland. Another weekend of traveling back and forth between the two houses. This intriguing structure sits along the Antwerp ring road traveling in the direction of Brussels and I've often thought I wanted to take a picture of it (from the passenger's seat, of course). I have no idea what this is, would say something to do with water management, but ... as far as I can see on the map there's no water anywhere near it. As so many structures along the motorway it's been covered by graffiti.

Edited to add that WilArt has explained that these are some kind of air ventilation devices for the Antwerp premetro lines, of the unused part of the subterranean tramlines for Antwerp.

Thanks very much for your lively comments and stars on yesterday's magnolia petal fall :-)