Pretty sure this is the castle they mean.
Built by the Knights Templar, it's in Castelo Branco, which, in case you don't speak Portuguese, means White Castle.
I've spent over twenty years worth of nights living in the region.
The dragons are busy playing with their new lenses and shining lasers all over the place at the moment, but I might try to find a way to get them interested in their own version of the song. They seem to like plagiarising poetry so I'm sure a parody would appeal to them.
The rocket mass heater is occupied by a (currently sleeping) dragon called Cuca, who emerges every spring to go and do battle with St George up in Monção. I suspect she's thinking of waking up soon and maybe she'll inspire them to write about her annual adventures. She generally loses an ear or two and has to retreat somewhere safe for the summer to let them grow back...
This is her losing this year's ear. I might go and see if she's waking up yet and check that it's grown back properly...
And as for what the knights in white sat in, I guess it was their saddles..
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