Today I found maps on the Guardian website which show the percentages of speakers of languages other than English in a number of major UK cities. It is based on data from the 2011 census and shows where the speakers are concentrated. For example, the main concentration of Bengali speakers is in East London around Mile End, while Arabic speaks are concentrated mainly along Edgeware Road. Meanwhile in Cardiff there are Polish speakers in most parts of the city with a particular concentration between Newport Road and Broadway.
This kind of map might be useful if you’re looking for people to practice your languages with.
Do you know if similar maps are available for other cities or countries?