As we drove our rental car into the parking lot outside Mexico’s Xochicalco archaeological site, an immense white butterfly, the size of my husband’s large hands, hovered overhead. The luminous creature seemed to guide us toward the stone steps leading to the ruins. The splendor of this elegant emissary and its unexpectedness seemed to symbolize our exploration of Mexican culture — past and present — in the foothills of the Sierra Madre mountains, south of Mexico City.

My husband, Eric, and I clambered up the steep stair-steps of a pyramid, aiming for the summit. Yet, as with scrambling up a mountainside, once we arrived there, we found that it wasn’t the true summit: At the far end of the high, parade ground–like terrace we stood on was yet another pyramid, soaring even higher into the sky.

“It’s a pyramid atop a pyramid!” pronounced Eric.

Stone viewing seats edged the sides of the field, with more seating seemingly available on the steps of the rear pyramid. I imagined a magnificently garbed Toltec king and his entourage watching a competitive ball game from their royal “box seats.”

Xochicalo’s Temple of Quetzalcóatl features a carving of the feathered serpent.

We crossed the greensward, and then stepped up the tall stone blocks of the smaller pyramid at the back of the field, which seemed to brush the sky’s vast blue dome. Large blue morning glories tangled in treetops twined up the sides of the structure. The high mountain air was still and humid, and I brushed a strand of hair off my sticky neck.

Trudging slowly upward, we passed what appeared to be guards’ quarters, before emerging at the top. Up here, where they could catch any stray breezes, and seemingly miles above any enemies, was where the royalty lived.

Walkways leading off in various directions led to a catacomb of small stone rooms; those with stone benches at one end were obviously sleeping quarters. I could imagine the numerous royal children lingering near the cooking quarters in the center, which featured doorways going off in opposite directions to tiny patios.

When we reached the far end of the rooms, I peered over a stone wall and gasped. It was a sheer drop of hundreds of feet to a forest of pine and oak, shielding the occupants from any enemies that might attempt to attack this stronghold. The view of undulating forest canopy was broad, perhaps 20 miles (32 km) distant, to a set of rolling hills.

As we headed back down, one of the stone rooms was different from the others. Seen from above, it resembled a regular oblong-shaped room, yet the entrance was a tunnel just big enough to wriggle through. The mystery tugged at me until I crouched down and belly-crawled through the opening. Inside it was unremarkable, except for its high walls with no door. A storage room for grain? A child’s room? An isolation room for punishment? Who knows?

The ruins hold many mysteries yet to solve. Yet what is known is that Xochicalco (meaning “in the place of the house of flowers” in the Nahuatl language, which is still spoken throughout Mexico) was occupied beginning around 200 B.C., and it reached its apex architecturally between A.D. 700 and 1000, after the fall of Teotihuacán, near Mexico city. Some speculate that this kingdom of some 20,000 residents may even have participated in the downfall of Teotihuacán.

In fact, one of the pyramids here holds the same carved deity as one found at Teotihuacán, a reminder of the influence the two sites had on each other: The intricately carved, undulating serpent on the Temple of Quetzalcóatl (which means feathered serpent), a major deity of ancient Mexico, is an exquisite piece of art. Between the arched curves of the serpent’s body are carved portraits of individuals, assumed to be the rulers who founded Xochicalco.

Carved stelae lay on the grass in one plaza, toppled by time and the elements. We attempted to decipher the faint patterns worn nearly smooth by the relentless sun and dry, high-mountain winds. Numerous stone outer buildings spread out on terraces at the foot of the ceremonial pyramid, from palaces to yet more step-style pyramids, from ball courts to a circular set of altars, and even an underground observatory.