London. Of course I may be biased but I think it's the most varied and cosmopolitan city in the world. I have travelled all over the world and I've barely seen a city that can match the variety of architecture, neighbourhoods, and people as London. I love the parks, the river, and the architectural contrasts between the grand Victoriana and contemporary glass and steel. The nightlife, culture, entertainment, and restaurant scenes are superb too - arguably the most varied in the world.