Translation:Is this the oldest prison in the country?
'Is this the oldest prison in this country' ? I know, there is no such thing like 'ten' or so here, but context can cast the spell. Although there is the English word combination 'in town', 'in country' does not work. 'In town' can often mean already referred to and most likely the speaker is in it himself. That's the same reason why I'd think that 'this' should be a valid translation, as I see no grammatical difference between 'w kraju' and 'w mieście' (?) - or does that not work?
Well, normally we don't accept such 'this' which is an addition (as there isn't any determiner in the Polish sentence), but in this example I have to say that it makes a lot of sense. Added now.