Though it's long been known to locals that something—something big—is buried in this patch of Guatemalan rain forest, it's only now that archaeologists are able to begin teasing out what exactly Head of Stone was.

Using GPS and electronic distance-measurement technology last year, the researchers plotted the locations and elevations of a seven-story-tall pyramid, an astronomical observatory, a ritual ball court, several stone residences, and other structures.

(See National Geographic pictures of excavated Maya cities.)

Some of the stone houses, said study leader Brigitte Kovacevich, may have doubled as burial chambers for the city's early kings.

"Oftentimes archaeologists are looking at the biggest pyramids or temples to find the tombs of early kings, but during this Late-Middle Preclassic period"—roughly 600 B.C.