Cities can, of course, be vast deserts of concrete or utility grass which offer no support to wildife. So it's good to see various moves to make cities and town more wildlife friendly (taking 'wildlife' in the widest sense including invertebrates!) .
One way of doing this is by sowings of mixed annuals such as these small beds in the centre of Berlin: annuals, perennial, shrubs and grass which isn't mowed too much!
It is being done on a grander scale in my own city, many hectares of grassland on housing estates are livened up by sowings of annuals:
Such sowings not only provide a basic (if eccentric) habitat for animals but they provide useful islands for migrating animals.
Should be noted that these are mainly exotic (non-native) plants - gives a much longer nectar, pollen and seed period.