"Not that exciting, once you get used to traveling so fast," says Iman lightly. "The ones underground here are all pretty grimy and loud and crowded. Everything smells terrible. They're incredibly un-glamorous. But that's sort of in the spirit of New York. And they are very convenient. I'll take you on one, if you want - you shouldn't go alone your first time, it can be overwhelming. For one thing the maps down there are way different. They don't correspond to the streets."

She can sense Greta getting tired, and tilts her head down. "You sure you don't want to rest some more?"