The weather turned balmy this week, above freezing even, and so I shed layers and took the iPod to work yesterday, the extra spring in my step brought to you by early Björk, Danger Mouse and by the disappearance of the ice sheets that until a few days ago extracted regular Bambi impersonations from unwitting pedestrians.

Björk’s happy happy Big Time Sensuality [iTunes] was playing when I got off the subway at Gamla Stan, and then as I passed the turnstyles I got a sudden sense of deja vu. I’d done this before. More specifically, I’d heard this song before as I exited a subway on my way to work, but not here — in New York, Cortlandt Street Station, getting off the N/R line coming down Broadway and about to take my commute through the bowels of the World Trade CenterNot, of course, on my iPod, but on my Rio 600. iPods are strictly a post 9/11 phenomenon — they were introduced in Oct 2001. Since it is hard to imagine life before iPod, I predict we will soon be spotting anachronisms in period films set in pre-9/11 New York, with iPod-toting actors jogging past WTC-intact skylines..

Over the past two and a half years I have often thought back to the human geography of those buildings, especially the mall through which I walked twice a weekday for 4 years until September 10, 2001. I’d always be among the first passengers out the gate, having made sure to board the train at the right spot. Once on the concourse, I’d aim straight for the North Tower on the other end, which meant cutting obliquely across a wash of PATH train commuters brimming up from the depths along steep, wide escalators. They were from New Jersey, I knew, which is why it was tempting to think of them as living on some Dantesque level of hell below, being summoned to work for the day.

Every day, I’d pass the same stores: First, a newstand on the right, source of my weekly Economist, then a J.Crew, where I bought a turtleneck sweater I finally wore out a few weeks back. On the left, Chase Manhattan bank machines, followed by a slew of cosmetics stores. Then, past the PATH, on the right, a GAP, a science gadget store, a souvernir store, and a deli that sold obscenely large Bacci chocolate assortments, no doubt to guidos crawling home to the wife after some infidelity at the office.

I’d then take the revolving doors into the North Tower lobby, and cut across a corner to the footbridge to the World Financial Center, where I worked. Every time I crossed that bridge I marvelled at how tempting a target it could be to terrorists. Blow this up, I would think to myself, and you’d kill scores and block a major New York traffic artery. How spectacularly clueless of me.

Yesterday, as I walked the tunnel that leads from Gamla Stan station to the street, I also walked the old commute in my mind. Björk’s big brash voice led the way in both places. It was good to be there.