Pumapunku

The largest stone at Pumapunku is a sandstone slab 8.12 meters long, 3.86 meters wide, and 1.2 meters thick, about 83 metric tons. It is one of 17 foundation slabs quarried in the Quimsachata range to the south. On top of them stood a building of about 150 andesite blocks. The andesite came from across Lake Titicaca, most likely from Cerro Khapia on the Peruvian side, where dozens of raw and half-worked blocks still lie along the routes down to the shore.

A 2023 model built from 102 radiocarbon dates puts the start of construction at about AD 580 and the last use of freshly quarried, carved stone at about AD 630. Its authors suggest that "perhaps only one or two generations of masons were responsible for most of Tiwanaku's iconic stonework." Building at Pumapunku ended around AD 710.

The H-blocks

Each H-stone measures roughly 97 by 99 by 55 centimeters and weighs about 600 kilograms. Jean-Pierre Protzen and Stella Nair, whose 2013 study of Tiwanaku stonework measured the blocks to within 1 millimeter, found that "many stones are perfect replicas of each other," while some that look identical "show significant dimensional variations." Some come in left-handed and right-handed versions. Their reading is that the H-stones formed a row of blind miniature gateways.

The stones carry the marks of how they were made. Protzen and Nair recorded pounding scars from hammerstones, point-chisel marks 2 to 4 centimeters long on a lintel, and, on one Pumapunku fragment, "a rare mistake" where a carving blade ran past the corner. H-stones in the field sit at different stages of carving.

Nair tested the method. Working a volcanic stone close to the andesite with tools of flint, agate, jasper, obsidian, quartzite, and hematite, she reproduced the precision, the right angles, and the sharp edges and corners of half a cross motif in about 40 hours. She could not match the flatness of the smallest interior surfaces. The study's conclusion is "No fancy theory is needed to explain Tiahuanaco stone carving."

Some joints were locked with metal cramps. Excavators in 1989 found two still in place in the channel walls, where the walls slope about 12 degrees and the cramps sit level, so the metal was poured molten into sockets cut across the joint. The alloy is copper, arsenic, and nickel. Heather Lechtman, who analyzed the Pumapunku cramps, has not located a source for the nickel.

The ancient-astronaut claims

Erich von Däniken's Chariots of the Gods (1968) described 100-ton sandstone blocks "topped with other 60-ton blocks" and stone conduits "scattered about on the ground like toys, obviously by a catastrophe." No earthquake or other catastrophe is documented at the site. The History Channel's Ancient Aliens later gave Pumapunku an episode, and posts online now say the H-blocks were cut to micron precision that only lasers or diamonds could achieve. The finest published measurements of the stones are to 1 millimeter.

Damage

The building was never finished. Bernabé Cobo, passing in 1610 and again around 1620, saw a gateway still standing on the largest slab. He wrote that Spaniards digging for rumored gold had done the most to ruin it, and its stones went into the church at Tiwanaku and houses in La Paz. When the Guaqui to La Paz railroad was built through the site in the early 1900s, carved blocks across Tiwanaku were blown up with dynamite for ballast. Around 1911, Adolph Bandelier found the platform "ruthlessly shattered for the purpose of treasure-seeking."

In 2006, a government project leveled the slabs and reset blocks in places they had never stood. Looking at photographs from 2008, Protzen and Nair asked why H-stones were sitting on the platform's "armrests." Most recent photographs of the H-blocks show them where that project placed them.

What remains unknown

In 2018, Alexei Vranich printed the surviving stones at 4 percent scale and fitted them back together. Only the gateways on the east side could be placed with confidence. He wrote that the model gave "a solid piece of evidence to rebut the mildly irritating persistent claims by ancient alien enthusiasts," because its form follows earlier buildings at Chiripa and Pukara. Nobody has worked out how the andesite building sat on its slabs, what it was for, or why the carving stopped after perhaps a generation or two.

Tickets cost Bs 100 for foreign visitors and Bs 15 for Bolivian nationals, cash only at the site, and cover Pumapunku, the main Tiwanaku complex, and the two site museums. Pumapunku is a short walk from the museums. The site administration lists hours as 9am to 4pm daily, while the municipal tourism office gives 9am to 5pm, so a morning arrival covers both.

Minibuses leave La Paz from near the Cementerio General, and the trip takes 1.5 to 2 hours by minibus or car. The site sits at about 3,850 meters. Paths at Pumapunku are marked, with rope barriers around parts of the platform.

In 2026, nearly 50 days of blockades on the La Paz to Desaguadero road, the route to Tiwanaku, kept most visitors away until the road was reported clear on June 21. Blockades recur in Bolivia, and it's worth checking the road's status before setting out. In a normal year, the Andean New Year on June 21 draws 10,000 to 15,000 people to the site.

The Fuente Magna, a stone bowl tied to the same lake basin, is on display in La Paz at the Museo de Metales Preciosos Precolombinos.