[Image: As if a lighter-than-air geometric fluid became temporarily frozen between two gateways of masonry, it’s just a bridge over the Norderelbe in Hamburg, Germany; photograph by Georg Koppmann (1888) from the collection of the Hamburg Museum, via Hamburger Architektur Sommer 2015, as spotted by Wassmann Foundation].
Dear Geoff,
the german Wikipedia page on the bridges over the Elbe has some more details:
https://de.wikipedia.org/wiki/Hamburger_Elbbrücken#Neue_Elbbr.C3.BCcke
There is actually a modern bridge reminiscent of the old sine wave, but without the nice portals.
All the best,
Alex
Thanks, Alex!