Learn Swedish: Officer Lars besökte staden där överste Anna bodde. - Officer Lars visited the city where Colonel Anna lived.

When a title, profession, or honorific is placed immediately before a person's proper name, Swedish uses the zero article, meaning it drops the article entirely. If you removed the names from this sentence, you would need the definite forms: Officeren besökte staden där översten bodde.

Why is där used for 'where' instead of var?

Var is strictly a question word used to ask a direct or indirect question about a location. When 'where' refers back to a place (meaning 'in which' or 'at which'), you must use the relative adverb där.

If we wanted to say Colonel Anna did not live there, where would inte go?

It would go before the verb: ...där överste Anna inte bodde. Because där överste Anna bodde is a subordinate clause, sentence adverbs like inte or alltid must come before the conjugated verb.

The word officer looks exactly like English. Is it an en-word or an ett-word, and how is it pluralized?

It is an en-word (en officer). However, its plural takes a very Swedish irregular form: officerare (and the definite plural is officerarna).