The Dead Beneath London’s Streets: Knowing this was a terrific inspiration for the Hawthorn House series. Everywhere you go in London, there are layers and layers of history, many of them burial sites.
Semiramis, legendary queen of Assyria: The original warrior queen, in a period where only the strongest killers survived. Me and historical research is a chicken-and-egg thing. Sure, I’m doing research for my writing. Yep. Definitely. (I have no idea what I’ll use this for but how can I not?)
Orbis, the Geospatial Map of the Roman Empire: Figure out how long it would take to get around the Roman Empire. Allows you to choose weather and land/sea options. No really, this is research.