Toledo Metro station in Naples

Picture: MARIO LAPORTA/AFP/Getty Images

Komsomolskaya metro station in Moscow

Picture: KIRILL KUDRYAVTSEV/AFP/Getty Images

Solna station in Stockholm

Picture: JONATHAN NACKSTRAND/AFP/Getty Images

Westminster Underground station in London

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The Arts et Métiers metro station in Paris

Picture: PATRICK KOVARIK/AFP/Getty Images

Westfriedhof station in Munich

Picture: CHRISTOF STACHE/AFP/Getty Images

The entrance to Bockenheimer Warte station in Frankfurt

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Mayakovskaya metro station in Moscow

Picture: KIRILL KUDRYAVTSEV/AFP/Getty Images

Olaias metro station in Lisbon

Picture: MIGUEL RIOPA/AFP/Getty Images

Avtovo Metro station in Saint Petersburg

Picture: Greg Balfour Evans / Alamy

Staromestska station in Prague

Picture: Michael Vasilyev / Alamy

Plac Wilsona station in Warsaw

Picture: JANEK SKARZYNSKI/AFP/Getty Images

Stadion station in Stockholm

Picture: JONATHAN NACKSTRAND/AFP/Getty Images

Auber metro station in Paris

Picture: PATRICK KOVARIK/AFP/Getty Images

Zoloti Vorota (Golden Gate) station in Kiev, Ukraine

Picture: SERGEI SUPINSKY/AFP/Getty Images

Materdei station in Naples

Picture: MARIO LAPORTA/AFP/Getty Images

Muenchner Freiheit station in Munich

Picture: CHRISTOF STACHE/AFP/Getty Images

North Greenwich station in London

Picture: qaphotos.com / Alamy

Heidelberger Platz station in Berlin

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Slavyansky Bulvar metro station in Moscow

Picture: KIRILL KUDRYAVTSEV/AFP/Getty Images

Kievskaya metro station in Moscow

Picture: KIRILL KUDRYAVTSEV/AFP/Getty Images

T-Centralen station in Stockholm

Picture: JONATHAN NACKSTRAND/AFP/Getty Images