Beijing was beautiful that day. The sky was a disconcerting blue, and the Blade Runner-esque skyscrapers were actually visible. The late summer sun formed streaks of sweat down our necks and a dryness in our throats. It glowed through the white curtains of the mercifully air conditioned expat apartment –professionally cleaned twice a week, I was told. And there, in the glaring brightness and sterility, was dark, grimy, beautiful Chicago.

The black-and-white photograph of the L was all lines and angles. You could fall into a picture like that if you looked long enough. The sharp gray shapes would become real steel and concrete and the ground beneath you would start to rumble as the train screamed past.

Where is this? I asked, though I already knew. It was more a question of surprise, like seeing an old friend again unexpectedly and they were changed but still, amazingly, exactly as you remembered. So you approach with open arms and disbelieving eyes. Is that really you?

Chicago: buying furniture with my mother at Goldblatts; walking along the frozen lake in February; sliding into the cracked green booths of our favorite Chinese restaurant. The restaurant closed after I left for college and I never found beef chow fun that deliciously smoky again. I am standing there watching the train go by above. The cold concrete beneath me is spotted with gum spots and pigeon poop. If you ask me the street name I won’t be able to tell you, but I know where I am. Everytime I go back, the city has changed –gained another glittering building or adornment, lost another historic name. But I know where I am.

The one day Beijing had blue skies and I missed the dust of Chicago.

Nostalgia was classified as a medical condition in the 17th century. Swiss boys fighting in France missed the mountains they grew up in and would waste away. Some even died. In the 18th century, scientists thought there might be a nostalgic bone. I suppose if they located it, they would remove it. Then those of us with wanderlust could truly be free.

My art historian best friend scoffed when I told her about the picture. It was the most generic photograph of a city she can think of, she said. Anyone can purchase a print like that for $29.99, plus tax, at some tourist shop or on Amazon.

I replied, So what?

When I looked at that little square of gray lines and shadows, I was in Chicago. And if anyone can own that accent of gray –and many people had bought these photos on Amazon– then that means all over the world there must be little windows to Home. I won’t waste away. And for $29.99 (plus tax) that’s not bad.