The ancient Greeks took around nine years to erect the Partheon on the rock outcropping that has since become known simply as the Acropolis in the center of Athens; their modern descendents have so far spent more than 30 years restoring and repairing the marble temple that towers over the Greek capital. For decades, visitors to the Acropolis have encountered jumbled scaffolding surrounding the Parthenon and the other ruins that sit atop the rock, and restoration will probably continue until 2020. Since the 1980s, more than 1,000 workers — including engineers, architects and archaeologists — have been working on the restoration, a 3-D puzzle in which the monuments are dismantled block by block and reassembled after thorough repair and cleanup.

Wear and tear has taken a toll since the temples were built roughly 2,500 years ago. Throughout the ages, the Parthenon, the Athena Nike and the Erechtheion temples have been burned down, bombed, hit by earthquakes, looted and vandalized. If not for this most recent large-scale rescue operation, which was initiated in 1975, the historical buildings would have been in serious danger of falling into complete disrepair.

The current restoration project has and figures of the pagan friezes were two goals. First, and most obviously, to restore the structures to their historical splendor and, second, to correct the subpar construction work of former restorations. Columns and walls that have collapsed or been reassembled incorrectly will be re-erected; marble blocks that have cracked or disappeared will be replaced; and more than 70,000 fragments of the Parthenon, which were scattered around the Acropolis rock, will be sorted out and put in the right places.

The work has required great care in part because the original temples were built with such accuracy that it is difficult to imitate, even with modern tools and machinery. In several places, the approximate space between the marble blocks is just four thousandths of an inch — less than a hair’s breadth — so when the blocks are reassembled, tiny margins count.

A DEVASTATING CANNON SHOT

Much of the worst damage to the Parthenon has come from human hands. The temple was finished in 438 BCE, and by 267 BCE, it was already under seige when parts of it were burned down. In the 500s, when the building was turned into a Christian church, several sculptures and figures of the pagan friezes were crushed, and the eastern main entrance was blocked up and replaced by a western entrance.

 In 1458 CE, after having been a church for almost a millennium, the Ottomans turned the Parthenon into a mosque and built a minaret on the western side of the temple. In spite of all of the changes, the Parthenon remained mostly intact until 1687 when Venetians attacked Athens, hitting the western facade of the structure with more than 700 cannonballs. One of them landed in an ammunitions room established by the Ottomans. Consequences were fatal: The chamber exploded, 28 columns were knocked down and the entire central section was destroyed.

After the explosion, looters descended on the crippled building. One of the most notorious was an Englishman, Lord Thomas Bruce Elgin, who took sculptures and friezes from the temple back to England, although he claimed to have taken them in order to protect them from ongoing conflicts between the Greeks and the Turks.

In recent history, air pollution has taken a toll on the marble monuments of the Acropolis, has as overuse by the massive number of tourists who visit the site each year. 

Paradoxically, former restoration efforts have done more harm than good. The worst examples occurred in the late 1800s and in the 1920s when the Greek civil engineer Nikolaos Balanos supervised two wide-ranging reconstruction projects of the almost-collapsed Parthenon.

Balanos was to strengthen the inner walls and re-erect the rows of columns that had been destroyed in the 1687 explosion. Balanos restored columns and walls but he ignored their original position, reassembling the marble blocks at random, which caused the structure to end up more damaged than before.

COMPUTER-AIDED WORK

In order to restore the building to its state before the cannon fire and explosion over 300 years ago, chief architect Manolis Korres and his team from the Acropolis Restoration Service have collected tens of thousands of original components, which have been scattered around the Acropolis for centuries. The marble blocks that are not cracked or damaged have been reused, and experts have recreated the missing fragments by using a computerized database in which all original fragments are recorded according to height, width, depth, incline, rust marks and damage. Based on that data, a computer has calculated where the fragments belong.

THE BLOCKS ONLY FIT IN ONE PLACE

The roughly 70,000 marble blocks of the Parthenon are customized; like the pieces of a puzzle, they only fit in one place. The original master builder deliberately aimed to make the temple lopsided in order to counteract the optical illusion that would have occurred if the structure’s floor and ceiling had been perfectly parallel. Unaltered, these lines would have appeared to sag when contrasted with the rest of the building. This so-called optical refinement is most evident in the temple platform, which is nearly 5 inches higher at the center of the long sides than in the four corners. Though these irregularities did the job that was intended, they’ve made restoration quite challenging for Korres and his team.

Just as in antiquity, the new marble blocks for the Parthenon are cut out of quarries on Mount Pentelikon, 12 miles northeast of Athens. Once they arrive at the construction site, the rough blocks are shaped in a workshop, with a 3-D plaster cast of the missing elements filling in the blanks. Stonecutters carefully shape the marble blocks using some of the same techniques as the ancient Greeks. However, some of the methods that the original artists used to shape the blocks so precisely remain a mystery. In some cases, not even the blade of a knife fits between them, and the original marks on the blocks indicate that the ancient Greeks had tools that were apparently both sharper and more durable than modern tools. 

COLUMNS WERE JOINED BY CEDAR

The restoration of the 46 outer columns of the Parthenon presents a different challenge for architects and workers. Each column weighs around 66 tons and is made up of 10 to 12 marble drums, which are lowered and placed in position one by one by a giant crane. The columns have never been dismantled before, and during the restoration, a 2,500-year-old secret was revealed. Originally, the drums were mated by carving two pieces of cedar, one fitting inside the other like a key into a lock. These pieces of wood were set into holes cut in the center of each drum.

When one drum was lowered onto the other, they were interlocked so accurately and snugly that the cavities still smell of the wood. The ancient lock mechanism has proved so efficient that it is also used today, although the cedar has been replaced by titanium.

LIVING COLOR

Familiar with the structure’s bright white facade, people may be surprised to learn that when the Parthenon was built, the temple was not the building seen today. The ancient Greeks painted the marble facade and the friezes in bright red, blue and green. When the facades were laser cleaned, hardly visible traces of paint were found here and there, which had long since been bleached by the sun and worn off by wear and tear. When restoration began in 1975, the Greeks were given the option to reintroduce color to the stark building but chose instead to rebuild the Parthenon to look the way it has for most of its 2,500-year life — like a majestic, shining white monument to the heyday of the ancient Greeks.