Q: This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.
The region covers an area of 1,579 square kilometres (610 sq mi). The population density is 5,177 inhabitants per square kilometre (13,410/sq mi), more than ten times that of any other British region. In terms of population, London is the 19th largest city and the 18th largest metropolitan region in the world. As of 2014[update], London has the largest number of billionaires (British Pound Sterling) in the world, with 72 residing in the city. London ranks as one of the most expensive cities in the world, alongside Tokyo and Moscow.
A:
With which two other cities is London named one of the most expensive in the world?