The Christmas favorites of Lego and Monopoly may still be popular this winter, but experts are predicting a boom for children's toys with more computer power.

Imagine a world where underground parks are the norm. That concept has become a real possibility thanks to James Ramsey. He's the creator of the Lowline, a project that, if all goes well, will turn an abandoned trolley terminal on the Lower East Side into a living, breathing, underground park by 20...