1. lots of water, both cities are literally constrained by the bodies of water that surround them

2. cultural centers of their respective areas

3. the ghetto is a VERY bad place to find yourself accidentally. although in paris, it seems like the army patrols the streets to keep the peace. i doubt that would fly in SF

4. there is shit on the sidewalks everywhere. in SF, it's from homeless people. in paris, it's because someone's dog did it and they didn't want to be bothered to pick it up

5. lots of homeless people begging for spare change, the only difference is that in paris the bums speak 5 different languages.