As far as I know, there isn’t really a place!
As far as I know, there isn’t really a place where beginners can go just to experience Kendo for an afternoon of fun. The All Japan Kendo Federation puts on a group event where you can go and experience holding the Kendo swords and trying on the armor. The event is once a month between 6 and 7pm, and is held at Budokan.
Anyone can participate in the event regardless of race, but children are not allowed to participate. There is some more information in English on this link here:
The Tokyo Kendo federation also puts on a similar event once a month, as well as a practice session only for viewers once a week.
The site is in Japanese, but you could have someone read it for you: