Medusa leads Sam through the front door of Milliways into her home. Her cave. Although, really, 'cave' doesn't quite cover it. It's cool, though, and directly in front of them is an open courtyard (the roof of that cavern had fallen in a thousand years before, and the girls had always been practical). There are blue tiles, mostly, all in perfect, quiet geometric patterns. Some potted plants, and a fountain (not drip, drip, drip - it's a proper wall fountain, steady as pouring out a jug). It's late afternoon, judging by the sun.
The other thing that is noticable is the magic. The girls have lived in that cave since the Sahara was an Eden of rivers and lakes, and in all those thousands of years, the magic has built up and up until it's a mesh of protection, safety, warding and comfort that not even the girls themselves really know how to unravel.
This is Medusa's home, though, and she knows it. What she doesn't know is the expression on Sam's face.