Ancient Engineering · Old City of Jerusalem

Western Wall Tunnel Megaliths

Hidden in a tunnel beside the Temple Mount lies a single limestone block longer than a bus and heavier than a fully loaded jumbo jet.

Mainstream: c. 19 BC onward (Herodian era)Alternative: Claimed by some to incorporate far older foundations31.78°, 35.23°

Engineering Belief

At a glance

Western Wall Tunnel Megaliths — Photo: David Shankbone · CC BY-SA 3.0

The Western Wall Tunnel runs along roughly 300 metres of the buried continuation of the Western Wall of Jerusalem's Temple Mount. Its most famous feature is the so-called Western Stone: a single ashlar 13.6 metres long and 3 metres high, with a hidden depth once estimated at up to 4.5 metres. Early estimates put its weight around 520-570 tonnes, though a later ground-penetrating radar survey suggested a slimmer block of perhaps 250-300 tonnes. Either way it ranks among the heaviest building blocks ever set in a wall, and it does not sit at ground level — it was placed within a rising course of masonry.

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The mainstream view

What archaeology says

Archaeologists attribute the Western Stone and its 'Master Course' to Herod the Great's reconstruction of the Temple Mount, begun around 19 BC — one of the largest building projects of the Roman world. The block is local meleke limestone, quarried close to the city and slightly uphill of the Temple Mount, so the stones could be moved largely on the level or downhill on rollers and sledges pulled by oxen. The distinctive Herodian dressing — flat central boss framed by narrow drafted margins — matches Herodian masonry across the region, from Hebron's Cave of the Patriarchs enclosure to Herodium.

Engineering studies suggest the giant course was structural: massive headers stabilised the wall against earth pressure from the vaulted fills behind it, and the sheer mass locked the lower courses in place without mortar. Roman-era lifting technology — cranes, capstans, lewis holes, levers and earthen ramps — is well documented by Vitruvius and by surviving hardware elsewhere; for the very largest blocks, builders likely used ramps and rollers rather than lifting them free of the ground.

Excavations in the tunnel, including quarries found north of the Temple Mount with partially detached blocks of comparable scale, support local extraction and short-distance transport during the late first century BC.

Key evidence cited

The drafted-margin-and-boss dressing matches securely dated Herodian masonry at Hebron, Herodium and elsewhere
Josephus describes Herod's Temple Mount project and the enormous stones used in it
Local meleke limestone quarries north of the Old City, uphill of the site, held partially detached mega-blocks
Transport was mostly level or downhill, feasible with rollers, sledges, oxen and capstans
The massive course functions structurally, buttressing the wall against fill pressure behind it
Coins and pottery in construction fills beneath associated Herodian streets date the work to the late 1st century BC and after

The alternative view

What the skeptics propose

Alternative writers frequently group the Western Stone with the megaliths of Baalbek in Lebanon — another Roman-attributed site with vastly larger blocks — and argue that classical-era cranes and ramps were not demonstrably capable of handling stones in the 500-tonne class. If the higher weight estimate is right, the Western Stone would outweigh anything Roman engineering manuals explicitly describe being moved.

Some fringe researchers go further, proposing that the lowest megalithic courses of the Temple Mount platform pre-date Herod — remnants of an earlier, possibly Solomonic or even pre-Israelite structure that Herod merely refaced and built upon. They point out that the biggest stones sit not at the very bottom but part-way up the wall, which they see as a puzzle for conventional construction sequencing, and note that the exact method used for this specific block is nowhere recorded.

Mainstream archaeologists respond that the masonry style is unambiguously Herodian, that placing the heaviest course a few metres above bedrock is sound engineering over uneven foundations, and that Baalbek-scale Roman megalithic transport, while remarkable, is attested by the quarried blocks still lying in situ there.

Key evidence cited

At 250-570 tonnes, the stone exceeds any load explicitly documented for Roman-era cranes
The precise method of placing this particular block is unrecorded, leaving room for speculation
Comparisons with Baalbek's 800-tonne trilithon suggest a shared megalithic tradition some argue pre-dates Rome
The heaviest stones sit above smaller lower courses, which some see as evidence of building atop an older wall
Joints in the Master Course are so tight that a knife blade cannot enter, despite the blocks' colossal size
No lifting bosses or lewis holes adequate for a 500-tonne lift are evident on the megalithic course

Genuinely open questions

What is the stone's true depth and weight — will further geophysical surveys settle the 250 vs 570 tonne question?
Exactly how did Herodian engineers place a block this size several metres above bedrock?
Do any pre-Herodian structural remains survive within the Temple Mount's lower courses?
Why did Herod's builders choose single mega-blocks rather than coursed smaller masonry at this point?

Worth knowing

Even at the lower radar-based estimate of around 250 tonnes, the Western Stone weighs more than a fully fuelled Boeing 747 — and it was set in place without an engine in sight.