that bar, on that Street, in that area

The same guys behind Bourne & Hollingsworth in Fitrovia have come up with an interesting concept called The Fourth Wall which is London's first wandering bar. It will be a replica of Bourne & Hollingsworth but in different locations every week, open every Friday and Saturday between 5pm - 1am.

The Fourth Wall’s weekly location remains a secret. Notes, emails, messages and codes will be left around London. What an innovative concept!

In the same vein, if you're in Amsterdam, go to Door74. A bar on a small side street, behind an unmarked, black door which serves the best cocktails in town. Make sure you call before though.