確かにそちらも書いてありますが…
マグリット美術館のHPの、「Opening hours」のところにあるのが
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TEMPORARY CLOSURE JANUARY 3rd > 31st, 2011
Due to improvement works of the HVAC installations (Heath Ventilation & Airco) the Musée Magritte Museum will be closed to the public from January 3rd to 31st, 2011.