Learn Hardcore Russian: Весь город знает эту историю.

весь means “whole” or “entire.” It’s an adjective modifying город and must agree with it in gender (masculine), number (singular) and case (nominative). Therefore we use весь (masc. nom. sg.). You could replace it with целый (as in целый город) without changing the meaning.

Why is город in the nominative case?

Because город is the subject of the verb знает. In Russian, the subject of a sentence stands in the nominative case.

Why is the verb знает in the 3rd‐person singular form, not plural?

Russian verbs agree with their subjects in person and number. Since город is a singular noun (the whole city, one entity), the verb takes the 3rd‐person singular form знает (he/it knows).

What case is эту историю, how is it formed, and why?

эту историю is in the accusative case because it’s the direct object of знает.

эта история (feminine nominative)
In the accusative, feminine inanimate nouns take the same ending as the nominative noun (историю vs история), while the demonstrative adjective эта changes to эту.

Can I drop эту and say Весь город знает историю?

Yes, you can. Without эту, you’re speaking more generally (“the whole city knows a story” or “knows stories”). Including эту makes it clear you mean “this specific story.”

Could I say Весь город знает об этой истории? What’s the nuance?

Yes, but the meaning shifts slightly.

знает эту историю = “knows (the details of) this story.”
знает об этой истории = “knows about this story” (i.e. is aware of its existence, but may not know all the details).

Can the word order change? For example, Город весь знает эту историю?

You could say it, but it sounds unusual or poetic. Standard order is Весь город знает эту историю. Placing весь after город or moving эту историю earlier will shift the emphasis or sound marked/poetic.

How do I pronounce this sentence? Where are the stresses?

Pronunciation with stress marks:
vʲesʲ ˈɡorət ˈzna.jet ˈɛtu is.tɐˈrʲi.ju
• весь [vʲesʲ] – stressed on the only syllable
• город [ˈɡorət] – stress on ГО-
• знает [ˈzna.jet] – stress on ЗНА-
• эту [ˈɛtu] – stress on Э-
• историю [is.tɐˈrʲi.ju] – stress on -РИ-