The Pokémon Go mobile game is the top-grossing app for Android and iPhone. Today, the U.S. Holocaust Museum and Arlington National Cemetery asked people to refrain from using the game while visiting the somber sites. Richard Vogel/AP hide caption

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In the Hall of Remembrance at the U.S. Holocaust Memorial Museum, visitors can light candles in memory of the 6 million Jews killed by the Nazis and their collaborators during World War II. Nicholas Kamm /AFP/Getty Images hide caption

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