The city's environmental record, along with its plethora of independent coffee shops, large farmers markets, friendly people and delicious food has made me a #1 fan.
A couple of my favorite food finds while I was there (recommended for when you visit) :
The Crumpet Shop - these spongy, porous muffin/pancake-y wonders can be topped with everything from nutella to eggs and ham to marmite and they are a wonderful texture, slightly crunchy, chewy and soft. Amazing. And the staff is super friendly.
Salumi - salami, salami, all kinds of peppered and fennel and sweet salami. Lines are always long, this place has the Bourdain stamp and the sandwiches are delish, but could use a little more salami.
Now what will it take for DC to be a top ten Smart City next year? They were only #31 this year. Interested to see how smart your city is? See rankings here.