1. Exposition

What was a royal city?

Joshua 10:2 (ESV)

2 he feared greatly, because Gibeon was a great city, like one of the royal cities, and because it was greater than Ai, and all its men were warriors.

This term probably identifies the city as being large and of some importance in the region. Gibeon is never identified as having a king, but we are told that it was larger than Ai and had good fighters.