This is the 7759th most frequent German word.
hartberg
"Hartberg" is a proper noun referring to a town in Austria.
Here, 'Hartberg' is used as a proper noun referring to a specific place.
Hartberg ist eine schöne Stadt in Österreich.
Hartberg is a beautiful town in Austria.
In this sentence, 'hart' is used as an adjective meaning 'harsh', and 'Berg' as a noun meaning 'mountain', combined to describe the climate.
Ich habe das harte Bergklima überstanden.
I endured the harsh mountain climate.
Here, 'Hartberg' again refers to the specific location in Austria, indicating place of residence.