The article

(The) first prize is a fortnight in Amsterdam and (the) second prize is a weekend in Rome. -- "the" is optional in both cases.

She took (the) second place in the long jump. -- "the" is not impossible, but the sentence is more natural without it.

Moscow is the second largest city in Russia. -- "the" is required.

Mr WordyMoscow is the second largest city in Russia. -- "the" is required.

Thanks again for your answers, Mr Wordy.

What if I put it another way?

Moscow is (the) Russia's second city.

Is it still necessary?

AnonymousMoscow is (the) Russia's second city.
Is it still necessary?

No, in this case "the" is wrong. You need:

"Moscow is Russia's second city."

Don't you just love English articles!

(By the way, these statements about Moscow appear not to be factually correct.)

Thank so much.

From all the examples, I think I have learnt something but I am not sure if it is right.

When we say

'Moscow is the second largest city in Russia', there seems to be a choice from a limited group of Russian cities. I think that's why we need 'the' to be specific.

When we say

'Moscow is Russia's second largest city', it seems that there

Articles are not used alongside the possessive form of nouns (e.g. "Russia's") unless the possessive noun (as opposed to the possessed noun) itself needs an article. It works in the same way as possessive pronouns ("my", "his", etc.). Just as you don't say "the my city" or "the his book", you don't say "the Russia's (second) city" or "the John's book".

However, "the Mormons' city" and "t