I find myself increasingly fascinated by the history of Dublin and Ireland, now that we've already gone and now that we're back. Before we left, of course, I was too busy getting my manuscript ready to learn about the place we were going. But onward, as there is plenty of time for self-recrimination later: for instance, we found out that Dublin was founded at the confluence of the Liffey and the River Poddle. The Poddle made settlement at the Dublin location possible--the Liffey is a freshwater river at its source, but in Dublin, it's tidal and therefore salty. The Poddle was a freshwater river; the confluence created a pool which gave Dublin its name (Dubh Linn = black pool).
But these days, the Poddle has gone, for the most part, underground. How does a river go underground? I asked myself, whilst in Dublin. Well, it turns out that this can happen a number of ways, including naturally, but it's also true that rivers can be diverted and culverted and even built over, which is what happened to the Poddle. (Also, the historian told me that he read an article by a guy who is interested in all the waterways in the Salt Lake Valley that have disappeared, gone underground, etc., and London has many streams and rivers, tributaries of the Thames, that have had a similar fate.)
Anyhow, there's a guy who's not only curious but kind of obsessed about this question regarding the Poddle. I am working on getting ready to think about writing a poem about a river going underground, maybe, but in the meanwhile, I'm looking at stuff like this:
(It's a little long, but that's the way it is with obsessions.)