Los Angeles - Sienna Miller could never live in Los Angeles - because prescription drugs are too easily available.
The British actress has been to Hollywood on several occasions for long periods of time, but says the lifestyle is not for her because she can see how easy it is to become addicted to medication.
She said: "Everyone's on something there. It's the most medicated place, there's a whole massive market for really addictive drugs. I've been prescribed Vicodin when I didn't really need it, It's dangerous. I mean, it's prescription heroin, really."
Sienna is currently pregnant with her first child with partner Tom Sturridge and once she has given birth she is keen to do more modern films as well as turning her hand to producing.
She said: "After the little thing [her baby], I'd like to do something modern next time because everything I've done so far has been set in the 1940s.
"It also makes sense to do your own stuff. I don't have massive aspirations to produce films, but I do enjoy that creative process of discovering scripts."