Possible alignments at Mycenae, Greece

The are nine tholoi around Mycenae/Mikines (in Peloponnese, Greece), but two are from the last (same) building period (1300 - 1200 BCE): Treasury of Atreus (also called Treasure of Atreus, Tomb of Agamemnon or T3) and  Tholos of Clytemnestra (T6). These two may have possible alignments (see a reference to my work by Schaefer [2000], page 131).
Region around Atreus
Region around Treasury of Atreus (made with GPS Visualizer)

The following stomion (passage) directions were measured (using compass and compensation in March 2004):
Name of tholos
(Spathari [2001])
direction []
Atreus, main dromos
Atreus, side chamber
Epano Phournos
Kato Phournos

Beside possible alignments also sound measurements (reverberation time: RT60) were done at the Treasury of Atreus (T3), T6, T11, T13, T14 and T15.

The below ideas are the result of the folowing visits: April 1998, June 1998, March 1999, March 2004, April 2007, April 2008, and Sept. 2009.

Possible equinox alignment at Treasury of Atreus

The location

The longitude and latitude of the Treasury of Atreus is:  22 45' east and 37 44' north both +/- 1'. It is build around 1250 BCE.

The horizon around the Treasury of Atreus

The horizon, formed by Mount Zara, seen from just in the covered passage (stomion) can be seen below:
A panorama picture made at the beginning of the dromos of this tholos, can be viewed as a normal picture.
You can see the following below:
  1. location of sunrise at summer solstice

  2. approximate location of sunrise at spring equinox

  3. The above sun (March 31st, 06:26 UTC = 09:26 local time) is almost at the same azimuth as sunrise on equinox.

Sun inside Treasury of Atreus.

The reason why the sun will be on the inside chamber wall, is explained with the following picture:

The picture let you see a compilation of three things:

As you see, the sky can be seen just at the back wall at eye height (there is bright sky light to be seen). The altitude from eye height near the back wall along the base of the triangular structure towards the outside its top, is around 22.8 +/- 1 (measured using clinometer):

Sun's path inside Atreus
Treusury of Atreus (Wace [1949], plate 5)

The maximum altitude that the sun light is still to be seen on the wall is presently at 23 45' +/- 5'.

The direction of the dromos is:

So with all this information, it can be deducted (using e.g. SkyMap) that the sun will shine two periods inside the chamber:
Furthermore the sun light looks to be in the chamber (at present times) for something like a month.

Modeling of the Treasury of Atreus

A 3D world around Treasury of Atreus has been made (the actual top of the hill opposite Treasury of Atreus is not yet visible in the world, I am working on this though).

An animation of the sun path on the back wall can be seen below:

Sunrise on June 20th, 1998

With the help of Vassilis Merekoulias and  Panagiotis Christias we proofed that the sun could not enter into the chamber on the longest day. The archeological office in Nafplion gratefully provided the permission to observe this from 06:30 local time. This experience let to the idea that the sun would get into the building around the equinoxes.

Sunrise on March 31st, 1999

On March 31st, 1999 video was made of the sunlight on the chamber wall.

Sunrise on Sept. 20th, 2002

On this day George Chronis, security office of Mycenae made pictures of the sun on the back wall, which is indeed within the predicted timeframe.
Sun on
        backwall on Sept. 20, 2002

Sunrises in March, 2004

To find out the first date the sun shines on the wall in March 2004, a journey was planned from March 10 until 17th 2004 to be sure the first light inside the chamber was in the middle of the trip. The following results where found:

Observations in September 2006 and March/April 2007

Shophia Terovola did observations of the sunlight in the chamber. I am very grateful for her effort and she provided permission to put these dates on this web page. Here are the dates:
That the sunlight was not seen before or after these dates could be due to clouded weather, no observation done or no possibility to have sun inside the chamber.
The declinations of these dates are fitting with the declinations found for the first day (March 15th, 2004) and the calculated end date (April 12th, 2007).

Sunrises in April, 2007

To find out the last date the sun shines on the wall in April 2007, a journey was planned from April 14 until 20th 2007 to try to catch the last light inside the chamber. The following results where found:
The present opening of the triangular structure is at its base some 17% smaller then originally (due to this small stone on the right):
Triangluar structure

This reduces the number of days the sun shines at present times inside the chamber from the calculated(/original?) 34 days to 28 days (so untill around April 12th). Remember beside this modern obstruction, the outside of the triangle has also changed (caved in/pushed up somewhat) and this would also considerably change the sky window of the triangular structure.

Sunrises in April, 2008

To really find out the last date the sun shines in present days on the wall, again a journey was planned now from April 8th until 14th 2008 to try to catch the last light inside the chamber. The following results where found:
Owl at T13

Sunrises in Sept, 2009

The aim of trip was to search for possible buildings on mount Zara (Google Earth might have revealed something; but it could be wishful thinking;-). But due to possible issues with snakes this has been postponed (winter time would be better). So only sun spot observations:

Reconstruction of the sky window of the triangular structure

!!!Paragraph still under construction!!!

The above observations of the sun spot on the back wall can be summarized in the below graph, where the start (light blue) and end (dark blue) azimuth and apparent altitude of the Sun have been plotted. The yellow curve is the apparent altitude of the horizon (due to mountain Zara).
observed altitude as function of azimuth

A computer model for the triangular structure and the tholos has been made and the resulting sky window is the space within the pink-ish line-form and the yellow horizon curve. You might wonder why the computer model is so close to the observations? This is because the input parameters of the computer model (height, width and length of the triangular structure) have been changed in such a way that it best maps the observations.

It is not that easy to measure in real live the in/outside of the triangular structure (unintended protruding rocks, shifted stones due to small cave-in/push-up over time, difficult to reach, precision needed, tourist/archaeological monument, etc.). This will need permission from the owners of the monument (Hellenic Minsitry of Culture) as a good precise size analysis will be needed. This permission will be seeked in the coming time (say for a winter time project?).

Two aspects have changed the sky window of the triangular structure over time:
  1. the slight cave in/push-up of several of the top stone layers (see the slightly moved stones at the top of the triangle).
  2. the modern obstruction in the right lower corner (since the 1950s).
If we assume that the above changes can be compensated for, then the sky window of former times will be larger. See below picture:

Skywonow of the
      former and present triangular structure

So some (not all!) explanation to the above picture:
With the present data (still investigating this though), we need an extra three days after(/earlier) equinox to see an increased lowest location of the sun spot.

As stated by  Heilbron [1999]: equinox alignments need to be build in sturdy and well settled buildings; so if the Treasury of Atreus was meant to be aligned with equinox, the relieving triangle did not survive the test of time fully;-).
The triangular structure of the tholos of Clytemnestra has stand much better the test of time (so they had the techynology).

If planning your own observations

It is important to write down if an observation was done and if the sun did not reach the wall due to clouds. A form and procedures is available.

Since when is the light in the chamber experienced?

There are a few accounts that it is known for quite some time:
It does not look like that it is known (widely) that this phenomena is around equinox.

Some conclusions

The apex of the triangle (in Athens, #1470) has on the right (but perhaps also on the left side) a clear ridge.
Hand drawing of
        'relieving' triangle
A sketchy picture of the apex
Such a ridge is not seen on other fragments seen in London (such as A.53, but it has a uneven surface in the middle band on the right side) or Athens (such as #1479).
If all these fragments are part of Treasury of Atreus, I don't know.

Possible geographical alignment at Tholos of Clytemnestra

In  the Tholos of Clytemnestra (some 500 m more to the north of the Treasury of Atreus and build around 1225 BCE) the triangular structure is on the inside fully closed up with big nicely cut and fitting stones, but in this case the dromos points to the south  (around 167.8), and it looks to be aligned with the mythological interesting mound at Nafplion: Palamidi. If weather permitting also the lower hill of Acronauplia is visible.
The mythology is: Palamides was the son of Clymene (which in turn was the daughter of Atreus or Catreus) and he died a tragic death, set up by his father (Nauplius)

triangular structure at Tholos of Clytemnestra

Vaguely the hill Palimidi is seen from just above the triangular structure,
in the direction of the dromos


I would like to thank Panagiotis Christias, George Chronis, Gregory Chronis, Agamemnon Dassis, George Dassis, Lesley Fitton, Peter Hastings, Dave Karr, David Mason, Natalia Merekoulias, Vassilis Merekoulias, Doug Schwartz and Shophia Terovola for helping me in getting all this information into daylight.

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Major content related changes: March 16th, 2004