Sadly, my current Thing Explainer book tour doesn’t stop in the UK (although you can come see me at London’s Royal Institution via live videolink on December 7th—tickets here).

However, in lieu of an in-person visit, my publisher and I have put together a special puzzle for UK readers to solve.

The puzzle has two steps. Step one is to find out where step two is.

For step one, you can pick any one of five cities. Here’s a helpful map, followed by some interesting facts about each city.