Until one day, I was travelling from Kilcullen to Newbridge along some backroads and I passed what turned out (after I checked some online maps!) to be the ruined harbour at Corbally. Click!
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A number of weeks since, I took an opportunity to take the camera out and make some picturegraphs to share. It looks like an old harbour, with some buildings next to it. What the buildings were for, I'm not sure, but they're pretty ruined now - maybe stores for a local business?
Of course, it was a beautiful day. I'd intended to walk along the canal, but poorly I chose the eastern bank and soon the way was blocked by gorse and brambles - the western towpath seems a bit easier, but if you're a sheep, leave your dog at home. (really though, there are sheep farmers here, so do leave your dogs at home!)
Further research (see links below!) notes that this is a feeder, much like Pollardstown Fen for the canal. It's about 5 miles out from Naas, so easily walkable with a picnic (though I say stay west, and check on maps first!).
Links:
http://iwai.ie/maps/grand/maps.grand.23.html
http://kildare.iwai.ie/
http://heritageboatassociation.ie/cms/index.php?option=com_content&task=view&id=352&Itemid=43