o
Sundial, calendar and Khmer temples

Astro-archaeology = archaeo-astronomy = Astroarchaeology = archaeoastronomy

Shrestrapura
 

An ancient Khmer city with equinoctial alignment

BACKGROUND:
     The author visited Champasak Province in Southern Laos two weeks in February 2006 in order to determine - by solar observations (sunrises) - the exact orientation of a) the processional road of the ancient Khmer temple Vat Phou and b) the barays (reservoirs) right east of Vat Phou.
     The ancient city, Shrestrapura, had since a previous visit 10 years ago been excavated and is presently being promoted as a tourist option. The location was anyway not marked in the field, so the author therefore used a few days exploring the area in order to map out the location and orientations of the surrounding walls of Shrestrapura. The spontaneous GPS measurements were later on follow up by studies of Hathena and ESDI satellite images. A procedure the other way around would have been more efficient.

ABSTRACT
     The construction of the ancient Khmer city, Shrestrapura, was initiated in the first part of the first millennium. A stone inscription discovered in Shrestrapura  mentions that King Devanika founded an administrative district in the second part of the 5th century AD. The construction of the lay-out of the settlement could well have been started centuries before. Only archaeological excavations can determine when the dikes were constructed.
     Shrestrapura is unique example of an ancient SE-Asian settlements with a carefully prepared urban layout. The centre line of the city is oriented straight true east towards the equinoctial point, from where the sun rises on equinox mornings. The southern and northern walls are neither parallel to the centre line nor to one another; they deviate respectively plus/minus app. 1 degree from true east.
     Other known contemporary settlements in nowadays Cambodia and NE-Thailand are generally surrounded by a circular moat/dike-system. Shrestrapura is not.
     The religious focal point of the Hindus living in and around Shrestrapura was the peak of the Phou Kau Mountain, Lingaparvata. The uppermost 10 m of the mountain resembles the linga - the phallic symbol of Shiva. This type of 'natural born' (Svāyambhuva) linga has been revered by the Hindu Khmers elsewhere as well. The Lingaparvata was the religious focal point of Shrestrapura, but not the geometric centre of the urban lay-out.
     Orienting and constructing a true east-west grid in the size of  Shrestrapura is not difficult. The construction only requires basic knowledge about astronomy. The compass was not yet invented, so the city-planners would have had to rely on the movements of the sun and most likely have used a gnomon (a vertical stick; a pointer). Rules for orienting a  Vedic altar using a gnomon were laid out in the previous millennium. The author does not use expressions like ''the cardinal points of the compass'' in relation to the orientation of ancient structures for two reasons. One is that the compass was not invented in the first millennium. Second that there is a difference between magnetic north and geographic north - called magnetic deviation.
     Knowledge about the use of the gnomon could have come from India together with the influx of religious concepts, but could as well have been in use before Indian culture influenced SE-Asia. The use of the gnomon is relatively simple and has been 'invented' and described other places in the same period (e.g. Greece). Determination of the first traces of a city-layout is interesting because the construction required basic knowledge in astronomy, a science that in India underwent fundamental changes in the first millennium.  The elder Vedic astronomy/astrology was replaced by newer books such as the Surya Siddhanta, which made school from the 6th century on. If influenced by Hindu tradition then the oldest part of Vat Phou would adhere to Vedic tradition and the later renovations from the 11-12th century adhere to the Siddhantic tradition..
     In the first part of the first millennium the Indian tradition for constructing Hindu temples generally was focussed on cave temples without significant astronomical orientation.
     Whether indigenous or not then the Khmers seem to have adhered to solar orientations in architectural designs to a greater extent than the Indians. And attributed with innovative astro-architectural concepts as embedded solstitial alignments (alignments towards the rising or setting point of the sun at the solstices) and solar-lunar alignments (as described here with Prasat Phanom Rung as an example).
     The author's working theory is that the Khmer rulers of the solar- and lunar-dynasties from the very beginning adhered to solar alignments (equinox and solstice) and later (Khleang-Baphoun) added innovations as solar-lunar alignments - all of it laid down in stone in the area around Phou Kao, Champasak.

HISTORICAL FRAME
     ''The oldest historical reference related to the Ancient City is found in the Sanskrit stele (K 365) dated to the second half of the 5th century AD. The text of the stele refers to the founding by King Devanika of a tirtha (or administrative district) called ‘Kurukshestra’, under the protection of Shiva in the form of Lingaparvata. Archaeological research has led to the Ancient City being identified as the city of Shresthapura. As such, the Ancient City is a unique example of early urbanism in Southeast Asia dating from the 5th to 7th centuries AD. Other inscriptions found in the area confirm the political importance of the Ancient City, which was probably founded by King Shrestravarman and which served as the capital of the Kingdom of Chenla until the reign of King Mahendravarman in the 7th century AD.''

Champasak Heritage Management Plan, 1999, p.74.
UNESCO Bangkok

Right: The stele - K 365

The centre line of Shrestrapura is oriented straight east-west.
There are no traces left of Shrestrapura's double walls towards east. They are eroded away by the Mekong river. The drawing above is the author's proposed original extension of the ancient Khmer city. A pedestal for religious ceremonies has been discovered on shallow water in the Mekong app. 400 m from the present western bank.

Shrestrapura: Shrestrapura means 'the city of  Shrestravarman' and dates to the 5th century.
Phou Kao: Phou Kao Mountain with its 'natural born' linga, the Lingaparvata.
Oumong: Oumong Temple (11th - 12th century).
Lek Cave: Tham Lek Cave hosts two inscriptions dating from the 7th and 8th centuries.
Vat Phou: Vat Phou Temple - alternatively written: Wat Phu. The eldest remains date to the 7th century.
Sida: Hong Sida Temple (11th - 12th century).
Lingapura: Lingapura means 'the city of lingas' and dates to the beginning of the 2nd millennium.
Thao Tao: Hong Thao Sida Temple. Jayavarman VII 'hospital' from late 12th to the beginning 13th century.
Tomo: Tomo Temple, where the oldest part dates to the 7th-8th century.
Linga: Lingas (Shiva's phallic symbol) are cut in the rock-floor app. 1 km SW from Tomo Temple.
 

Above: GPS-based 3-dimentional map of the area around Shrestrapura.
The centre line ('CL') of the ancient city nearly aligns Ban Loang Kao on the present riverfront with Tham Lek Cave and after passing mid between Phou Lek Temple and Phu Lek Mountain continues up the Khorat Plateau in the distance (with courtesy to Shinji Saito).

The author's interim interpretation of the concept of the urban lay-out:

Shrestrapura is orientated towards the equinoctially point and the Tham Lek cave might be the the 'hub of the Universe'
 

1) The urban lay-out is focussed on an orientation of a straight east-west centre-line - thereby making the whole structure oriented according to the cosmic order: The annual revolution of the sun. Solar observations from the centre line of any structure aligned towards the equinoctial point (from where the sun rises sun on equinox mornings) will tell the observer when a revolution of the sun has taken place. The re-occurrence of equinox day would be evident - and an eventual necessity for inserting e leap day would be similarly evident.
2) The sun would rise aligned with the southern walls app. 2 days before vernal equinox and rise aligned with the northern walls app. 2 days before autumnal equinox.

3) The Phou Kao - Tamo orientation is solstitial: At winter solstice an observer standing at Phou Kao will see the sun rise from behind Tomo.
4) Phou Kao, Tham Lek Cave and the Tomo Temple seem to be aligned (Tham Lek Cave was not visited, so the location is based on map readings). IF the Tham Lek Cave is located aligned with Phou Kao and Tomo AND at the same time also is located on the centre-line of Shrestrapura, then the Tham Lek Cave is the focal point geometrically, astronomically and conceptually: From the cave Surya, the Sun, will be seen rising behind Tomo (and Phou Asa) at winter solstice. At the equinoxes the sun rises aligned with Shestrapura.

Above: GPS-based map.
The ancient city has been drawn as the author suggests it to have been 1.500 years ago before the Mekong shifted course and eroded app. a third of the settlement.

The Phou Kao - Tham Lek - Tomo - Phou Asa alignment: Phou Asa is located 28.8 km SW of Phou Kao. A theory of a 'great alignment' is appealing, but the alignment can for several reasons not be regarded as significant: The present construction at Phou Asa is most likely not ancient Khmer. Phou Asa is not visible from Phou Kao - or the other way around. Tham Lek Cave is located app. 120 m south of the 'great alignment' and the centre line of Tomo 180 m south of. The orientation of the centre line of Tomo is not parallel with the 'great alignment', the deviation is 4 degrees.

 

On page 82 in Champasak Heritage Management Plan, 1999 UNESCO Bangkok we are supplied with a most competent interpretation of concept behind the urban lay-out of Shrestrapura:

''... the planning of the landscape reflects the religious beliefs and symbolic world view of its rulers. The use of the area is not purely utilitarian but strongly reflects the Hindu view of the world prevailing in the 5th to 12th centuries AD. Inspired by the natural linga at the peak of Phou Kao Mountain, the rulers of the area planned their world around it and engineered the landscape to conform to a very specific spiritual template. The Lingaparvata provided the focal point of the whole and symbolized Mount Kailasha, the sacred mountain dwelling of the god Shiva, while the Mekong River, the other great natural feature of the landscape, represented the Ganges River and the surrounding Universal Ocean. The plain between the mountain and the river formed Kurukshestra, the Holy Land. This is clear from the way in which the site’s features are laid out along an axis from the Lingaparvata through Shiva’s Temple at Vat Phou. This axis continues on through the monuments of the Ancient City and across the Mekong River to Tomo Temple where Shiva’s shakti Rudrani was enshrined. While this layout draws strongly on classic Hindu cosmology, at Champasak the template has been merged with an earlier Southeast Asian perception of the dualism of mountains and water which results in a distinctive regional interpretation of that cosmology.'' [my underlining].
 

Above: GPS-based map showing that the peak of Phou Kau, the Tham Lek Cave and Tomo Temple are nearly aligned. Vat Phou is more than 700 m of the alignment.

COMMENTS:
     There seems to be several weak points in the hypothesis quoted above. First and most important is that Phou Kao, Vat Phou and Tomo are not aligned. Second that the above mentioned 'axis' does not run through the monuments of the ancient city, Shrestrapura, where no monuments, dikes or moats share the orientation of the Phou Kao - Tomo orientation. Finally: The postulation of ''an earlier Southeast Asian perception of the dualism of mountains and water'' needs elaboration. We have no knowledge about ''Southeast Asian perception'' in the beginning of the first millennium.
     The two alignments at Vat Phou and the alignments of major temple structures with associated barays such as Nang Sida, Ban That, and Phu Lek should also be mentioned as they reflects the religious beliefs and symbolic world view of later Hindu rulers.

The alignments of Vat Phou

At Vat Phu there are two alignments:
1) The processional road
2) The eastern baray.

These are described elsewhere and will be the focus for Solar-Tour-2007 (itinerary is under preparation).