I visited the British Museum in December 2019.  Compared to the exhibits from other areas of the globe there is a modest African selection in the basement but includes some extremely valuable artefacts from outside of the Congo such as the 13th Century Benin Bronzes from the Edo peoples (shown below). 

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With respect to the Congo itself there are a number of exhibits including Kuba and Luba masks and a Katanga cross.  

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The world famous Museum is worth a visit of course and it has some excellent African artefacts.