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basin (e.g. between mountains)
京都は盆地なので夏はとても暑いですよ。
Kyoto is a basin, so summers are hot.
この盆地は農業に適した土地だそうです。
This basin is suitable for agriculture.
京都は盆地なので夏は特に蒸し暑い。
Kyoto is in a basin, so summers are especially humid.