This is the 6750th most frequent Japanese word.
ヒルズ
"Hills" (ヒルズ) refers to a development or complex, often upscale, typically featuring buildings, shops, or residences.
Here, 'ヒルズ' refers to 'Roppongi Hills,' a well-known complex of buildings in Tokyo, commonly used as a proper noun.
六本木ヒルズに行ったことがありますか？
Have you ever been to Roppongi Hills?
In this sentence, 'ヒルズ' is used generically to refer to a hilly area or region, metaphorically indicating residential development.
その地域には新しい住宅ヒルズが建設されています。
New residential hills are being constructed in that area.
'ヒルズ' here denotes a metaphorical or named geographic area that houses a building or locale.