It's French and was once 196m long in an almost O gauge size, must be a different feeling to be able to send a train off and for it to take many minutes to come round again.

http://metromodel.free.fr/modelisme-Maquette-de-lagny.htm

The Stuttgart N Convention pulled together a 500m modular system in 2007 - I have the T-shirt

I should have put the word "permanent" in the title

Doesn't Miniatur Wunderland trump everything? They've got the Guiness World record at 15,715m

There was also the Biggest Little Railway in the World which measured at 71 miles! (although this was track laid on the ground with nothing but natural scenery).

Steven B