Mycenaean Bridges; in constant operation for at least 3,000 years

The ancient bridges and their remnants located in the vicinity of Mycenae and Arkadico villages are considered to be the world’s oldest bridges. The bridges were built with massive irregular limestone blocks, called Cyclopean boulders, in the Bronze Age. Two of the four objects discussed here are still in operation, occasionally used for the needs of local agriculture.

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The ancient bridges similar to the Mycenaean bridges built in other continents in the centuries BC are scant. For example, the documented history reveals that the bridges built in China around 1200 BC, such as the floating bridges, are mostly made of wood. The unearthed archaeological evidences reveals that the bridges built in Xi’an, the capital of Shaanxi province, dating back to 200 BC approximately, were built with wood as well (See figure below).

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Leaving aside the priority of the clapper bridge, two bridges in the vicinity of Arkadico, Peloponnese, Greece, can be deemed the oldest existing bridges. They have not been precisely dated. The most often quoted period is the Bronze Age, i.e. 1,300 – 1,190 B.C. Both bridges are accessible to tourists and occasionally used in local agricultural transport. Apart from the aforementioned bridges in the Mycenae area, there are also remains of two other bridges to be found.

Location of the objects in question

A contemporary Google map showing Mycenaean settlement sites, two functioning bridges, and two Mycenaean bridge remains (figure below).

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The functioning bridges have touristic names. They are called as follows, respectively:

– Kazarma Bridge – Mycenaean bridge A (MB-A). (See figure below)

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– Petrogephyri Bridge – Mycenaean bridge B (MB-B). (See figure below)

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The bridges are situated along a Mycenaean road which links Mycenae, Tiryns, Tolo and Epidaurus – have linked before and links today, too. Today, the road is called Avenue Asclepius (Λεωφόρος Aσκληπιού) and runs together with the new road number 70.

In the village of Arkadico there is also a remnant of another Mycenaean bridge. In the Map, it is marked as MBR-1, after its full name, Mycenaean Bridge Residuum 1. In this case, only the structure of cyclopean boulders reminds of the ancient bridge of earlier times (See figure below).

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Right next to the water inflow side of the bridge, an agricultural road runs to the neighbouring olive groves (See figure below).

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In the technical sense, the bridge does not work at all. It is rather an unprotected archaeological site. There is no clear watercourse, although the ground is naturally moist. That proves the unchangeability of waterways since the Mycenaean times.
Nevertheless, two narrow openings – spans are easily noticeable. Currently, they do not function at all. Only the boulder system of the vaulting arch allows the presumption of their previous bridge function (See figures below). The two dimensions of cyclopean boulders give a metric reference to the dimensions of the whole structure.

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In the figures below, another remnant of a Mycenaean bridge is shown. In the Map, the place is marked as MBR-2. Visible fragments are situated in the mountain valley of a dry riverbed at the end of the contemporary Mycenae village. From the characteristic, small church of Agios Ioannis to the ancient Mycenae fortress runs a road about 1 km long, parallel to the valley.

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This monument has not been thoroughly described, therefore, the following photographs contain its basic dimensions, (See figures below). The width of the dry riverbed in the widest point amounts to approx. 40 m, which means that the width of the bridge was similar. Hence, it might be the longest Mycenaean bridge. Consequently, one can assume that it was a multi-span bridge.

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The width of the side Cyclopean boulder walls amounts approx. to 1 m. The maximum height, measured from the bottom of the dry watercourse, amounts up to 4.7 m.

Technology of Mycenaean bridges

In the bridge construction unwrought sizeable stones called Cyclopean boulders were used – a common building material in Peloponnese. They were marble – metamorphic rock resulting from the limestone metamorphosis.

In the construction of the bridges shown in the previous figures above, Cyclopean boulders of similar size were used. A fragment of the abutment is a complex structure. In the bottom part sizeable boulders were used, laid on a natural rocky ground. Above, a horizontal plate platform, providing stability for the bottom boulders and, at the same time, a basis for another layer of upper boulders, was noticeably put. The shapes of the outlines of the external surfaces resemble squares or vertical rectangles. Further above, there is another platform where, probably, stones constituting the road were placed. In modern terms, one can speak of mechanically stabilized rocks. It was not entirely possible to examine the scope of platforms, however, a lot points to the fact that the platforms formed surfaces on the whole horizontal cross-section of the abutment structure. If that were the case, the structure in question would be technically more advanced than bridges MB-A and MB-B.

Bridge MB-A is classified as a corbel bridge, despite the fact that its present condition corresponds to an arch bridge of a clumsy arch vault. Leaning towards the concept of corbel bridge, one can distinguish, with a high degree of arbitrariness, support plates through conjoining neighbouring boulders.

The bridge spandrels were made of chosen boulders, whereas their arrangement is chaotic, the bottom of the walls of the side abutments resembles the shape of the river bed. The riverbed is an artificial structure constituting a bottom slab. The use of a bottom slab which at the outlet forms a distinct, quite high threshold testifies to an extensive hydraulic experience of the constructor.

The bottom slab stabilised the walls of the bridge opening, reduced their washing out and, as a result, their horizontal movement. The structure of the bottom slab with a few characteristic element sizes is shown in the figures below.

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The MB-A bridge has two faces. Here, the following problem can be discussed: whether it is a corbel bridge or an arch bridge. In the case of the figure below one is almost forced to classify the bridge as an arch one, although some virtual fusion of “matching” neighbouring boulders is possible.

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Figure below shows a corbel bridge, without question. It can be concluded, therefore, that aiming at a support construction, the builders skilfully used accessible materials, arranging them to resemble primitive arch bridges. If that were the case, one can speak about a mixed technology – a corbel bridge and an arch bridge. A prerequisite for the application of the support scheme is a relative ease of drawing marble plates, even more so with regard to the fact that a perfect marble lubricant was available, i.e. water. With high probability approaching certainty, it can be assumed that in the support system it was not necessary to use scaffolding. Only fixing a boulder in the key required some rolling or a turn at the moment of placing it in its final position.

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The technology of the Cyclopean boulder arch bridge was much more demanding. Rolling subsequent boulders and putting them in position required temporary supports. Even if shores had been primitive and easy to arrange, the process required a good sense of the mass of elements and their weight. Nowadays, it is known as structural mechanics.

In the case of Mycenaean bridges, seismic influences combined with significant weights of Cyclopean boulders and a material which is not particularly resistant to shearing and bending, i.e. marble, result in systematic increase in boulder cracking and moving (See figures below).

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Seismic activity threatens the existence of MB-B. In one of the above figures, the areas of the greatest material stress, determined in the static analysis, are outlined in red.

Conclusions

Two among four Mycenaean bridges discussed in the paper have been in constant operation for at least 3,000 years. This fact puts them at the forefront of the most durable bridges in the world. The bridges were constructed with Cyclopean boulders. Their weight varies, although the heaviest ones weigh from 10 to 20 kN. The corbel bridge is assumed as the structural scheme, however, the conclusions indicate a mixed scheme. At certain points Cyclopean boulders were arranged according to the arch bridge scheme. Nevertheless, this conclusion can be undermined by the fact that the analyses concerned the present boulder configuration which may be a result of seismic activity. Similarly, the use of temporary scaffolding during the construction process can be presumed. In the case of the corbel bridge scheme, scaffolding might have been redundant until the moment of fixing the keystone. If the arch bridge technology had been used, there would exist no prerequisites for omitting scaffolding.

In constructional terms, bridge MB-B is threatened by a disaster. The application of protection measures is highly recommended.

Both functioning bridges and the remains of the other two bridges (MBR-1 and MBR-2) constitute the historical heritage of mankind. Despite this fact, none of them has been appropriately described or exhibited.

(Source: “The World’s Oldest Bridges – Mycenaean Bridges”, by Karas Slawomir, Nien-Tsu Tuan)

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Research-Selection for NovoScriptorium: Philaretus Homerides

 

 

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