Five fathoms

To add to Bonnie's songs of walking posts, here's Everything but the Girl walking the streets of London:

I walk the city late at night 

Does everyone here do the same?

...

There's a river in my head

Updated: I was wondering about the title of this song and my guess its a Tempest reference:

Full fathom five thy father lies; 

Of his bones are coral made; 

Those are pearls that were his eyes; 

Nothing of him that doth fade, 

But doth suffer a sea-change 

Into something rich and strange