Heading to Greece? You’ll want to swing by the Parthenon, one of the most alluring and structurally adventurous buildings ever conceived. This highlight of Athens’ Acropolis has seen better days, but work is ongoing to restore the ruins and reclaim its former glory.

Despite its current state of disrepair, however, the building itself presents a compelling constructive paradox: How did Athenian engineers find the balance between architectural beauty and structural brawn in this piece of ancient architecture?

Built to Last

The existing temple sits on the site of an older building that was razed by the Persians in approximately 480 BCE. As noted by the Encyclopedia Britannica, construction of second temple to Athena began in 447 BCE under the direction of Pericles. Architects Ictinus and Callicrates (also called Iktinos and Kallikrates, respectively) were called upon to create the building which would eventually house a 39-foot high marble statue of Athena holding a gold-and-ivory aegis and carrying 6-foot tall image of the goddess Nike in her other hand.

To construct the temple itself, Athenian builders hauled more than 100,000 tons of marble from a nearby quarry to the construction site where they were hand-trimmed and set in place. Experts believe the massive blocks were moved using a combination of pulleys, ropes and wood cranes — tools already available to the Athenians thanks to their existing naval ships. According to Smithsonian Magazine, the blocks were fastened together without mortar; instead, the Greeks used custom-built iron clamps set into meticulously-carved flutes. Lead was then poured onto the clamps, helping them withstand both regular earthquake events and prevent rusting. Civil engineering professor Kyriazis Pitilakis of the Aristotle University of Thessaloniki notes that the columns supporting the Parthenon “are designed so that they have excellent seismic performance properties.”

Perfect Imperfection

There’s no denying the beauty of this ancient engineering feat; while the bulk of the temple was constructed using the simple, clean lines of Doric architecture, other elements — such as columns supporting the inner chamber roof — used the more elaborate Ionic style. Along the top outside edge of building is a repeating pattern of three-channeled and carved square blocks, known as triglyphs and metopes. There are 92 metopes in all: Those on the north side show the Trojan War, the south a mythical battle with centaurs, the west a battle with giants and the east a battle against the Amazons. The inner chamber (cella) contained a horizontal decorated frieze that ran the length of the walls and used the bas-relief technique to raise the figures slightly from the background.

But for all its beauty, it’s also a building of intentional imperfections designed to trick the eye and improve the viewing experience. It contains no perfectly straight lines; instead, the builders attempted to account for the natural tendency of straight edges at scale to appear curved. To accomplish this, the columns lean slightly inwards and bulge subtly in the center, giving the illusion at distance of perfectly straight lines. In addition, the floor of the temple rises slightly in the center to make it appear flat to outside observers, and the four corner columns are slightly fatter than the others, making them seem equally-sized when accounting for the negative space beyond their edge.

Athena’s Got Talent(s)

Ancient architecture isn’t cheap — estimates put the cost of building the Parthenon at around 470 silver talents. While there’s no exchange rate between USD and Athenian talents, the city supposedly had gross annual income of just 1,000 talents with 6,000 held in reserve. For perspective, the cost to build and fully outfit the most advanced warship of the era — the trireme — was a single talent.

Sculptures and metopes also contributed to the overall cost and monumental amount of detail work needed to complete friezes. While the temple itself was dedicated in 438, work continued on the artistic elements until 432 BCE. For example, a stippling pattern applied to the marble which helped dull the finish and reduce the appearance of imperfections “may have taken as much as a quarter of the total construction time expended on the monument,” according to Manolis Korres, formerly the Parthenon’s head restoration coordinator.

In fact, modern efforts to restore friezes and columns have been hampered by technical limitations that would make such a project outrageously expensive in this day and age. While the use of a flute-carving machine has helped speed the process of repair, the precise detail needed to ensure a perfect fit demands hand-chiseling at the final stage. There’s also evidence to suggest that current tools can’t match ancient chisels and axes for sharpness and durability, meaning Athenian workers were getting more done, faster than tech-driven restoration efforts — and still needed 15 years to finish the job.

Boom Goes the Dynamite

Beyond the wear and tear that comes with 2,000 years of history, why is this feat of ancient architecture a shell of its former self? As noted by History.com, it started when Christian Byzantines conquered Greece in the sixth century and outlawed pagan worship. They converted the temple into a Christian church and blocked the east side entrance. In 1458, the Ottoman Empire took Athens and converted the church into a mosque — but when war came to their doorstep in 1687, the Empire decided to stockpile ammunition inside. Under heavy cannon fire, stored munitions exploded and much of the temple was destroyed.

The Sincerest Form of Flattery

As noted above, restoration efforts are underway — they began in 1975 with $23 million in backing from the Greek government. Initial estimations suggested the repairs could be completed in 10 years, but speedy (and sloppy) work done in 1898 proved problematic, causing columns to swell, crack and shift and necessitating immediate replacement. A focus on reusing the original materials wherever possible has also slowed progress; it took architects more than five years to identify the positions of over 500 blocks scattered around the Acropolis thanks to the munitions stockpile explosion.

While work remains underway — and behind schedule — a full-scale replica of the Parthenon already exists in Nashville, Tennessee. Functioning as the city’s art museum, it features direct plaster casts of original sculptures and monuments to provide a modern, tangible interpretation of Ancient Greek beauty and brawn.

From the Parthenon to the pyramids, the Taj Mahal to Rome’s Colosseum, ancient architecture remains both culturally relevant and mechanically mesmerizing.