Videogames/Arcades/Retrogames in Cologne (Germany)?

[Shin Daisuke]

Hi guys! Don't know if it's the right section, if not I'm sorry for the mistake.

The next week I'll take a trip to Cologne, Germany (I'll be attending the "Symphonic Fantasies" concert).
Does anyone of you know if there's some arcades, videogaming (especially retrogaming) shops - or even some flea market - to visit while staying there?

Thanks in advance guys!