Need I say more guys? Time by time, through our apartment window I can spot some discreet types tip-toeing across a particular rooftop. A few quick steps, a tossed towel and splash—they are in their rooftop hot tub. Oh, the jealousy!

So to spread the feeling around, here are some of my favourite vintage shots of thermal pools from Nat Geo's excellent tumblr, Found.

The best natural hot springs I've had the chance to dip into would have to be Iceland's Blue Lagoon, Bagni Vecchi in the Italian Alps, and perhaps the onsen at the old ryokan near Jigokudani Park in Japan. And today, my bath, I guess...

How about you?