One of the first questions that can be asked, concerning the "pyramid of the Sun", is that of its exact shape. Indeed, the "perfect" shape of Visocica is often stressed by Mr. Osmanagic, and is used as "proof" of its artificial nature (meaning: nature cannot have produced so perfect a shape): see for instance the first paragraph in the document "Naucni argumenti" - "Scientific arguments", published in May 2006 on the Fondation website (it can be downloaded here (bs) ), called "A perfect geometry" (an english version of this "report" can be downloaded there (en)).
In Mr. Osmanagic’s book (bs) it is said to be a pyramid with four faces oriented toward the cardinal points, this fact being confirmed by a not yet published (but partially used in the document "Naucni argumenti") report by the "Institute of Geodesy of Bosnia and Herzegovina" (of which one member, Mr. Enver Buza, is "adviser" for the Foundation); the same document adds that the North face is oriented "toward the celestial North". Mr. Osmanagic indeed stresses in his book that "all the other pyramids in the world are equally oriented toward the cardinal points".
First comment on these assertions: it is easy to find examples of pyramids not oriented toward the cardinal points. Here is for instance the pyramid of the Sun in Teotihuacan, it’s easy to see that it is not oriented at all toward the North !
Second comment: claiming that the North face of Visocica is oriented toward the "cosmic North" doesn’t make a lot of sense scientifically . Mr. Osmanagic and his team sometimes claim that Visocica is "oriented toward the North star" (or Polaris) . However, because of the Precession of the equinoxes (en), the celestial poles are slowly moving. If, today, Polaris approximatively marks the place of the North celestial pole, it was not the case 12,000 years ago (proclaimed age of the pyramid). At that time, the North celestial pole was very near to Vega (see this map showing the slow rotation of the North celestial pole during a period of about 25,000 years). The fact that Visocica is "oriented toward Polaris" is nothing more than a coincidence. But let’s admit that they just wanted to say, quite awkwardly, that the North face of Visocica is exactly oriented toward the North: it seems to me that the "exactitude" of this orientation is far from perfect! One can judge with these two documents, from the geophysical analysis (en)  made by Dr Smailbegovic in February 2006:
On this detailed map, one can notice that the contour-lines on the North face are not perpendicular to the direction of the North, as should be the case if that North face was exactly oriented toward the North.
On this second document, it can be seen that the orientation of the most frequent lineaments marking the North-East and North-West angles, as seen by the LINANAL detector, are not symetrical on each side of the North direction: on the North-West they are oriented N35°W, and on the North-East N45°E.
Third comment: a look at the topographic map of Visocica is interesting:
At first look, the least that can be said is that the pyramidal shape is not very visible. East face and especially North face (the one that is most often shown on photographs) are actually quite triangular, but it is much more difficult to identify a South face, and moreover a West one. The Foundation is explaining this fact by the existence of an "access plateau" to the pyramid on the West face (plateau that is therefore artificial as well), and by "erosion" on the South and West face, with no precision as to the kind and origin of this erosion (in fact, they should more talk of "deposits" after the building of the pyramid, as one can clearly see that there is an excess of material on this place, and not missing material that would have been taken off for instance by fluvial erosion). See the interpretation given by the Foundation:
On can notice that, on this "reconstitution", the South-East angle as well as the South-West one have been placed in a totally arbitrary way (of course, as they are eroded...), and even like that the least that can be said is that the four faces are quite unequal. I have attempted my own reconstitution of the angles using the topographic map:
I can see at the most three angles, there is no South-West angle on the map.
Now, if I try to put on the map the points of intersection between one contour line and each angle, and to link these points, I should theoretically obtain something more or less squared, like here in Teotihuacan:
If I try the same thing for Visocica (here for the contour lines of 550 m and 700 m), I’m obtaining something very different from a square...:
You will object that my reconstitution is debatable, but it is not more debatable than the one suggested by the Foundation! Apart from the North face and the North-West and North-Est angles that are quite clear, the other faces and angles are a lot too dubious for a "perfect geometry" to be used as "evidence" of the pyramid.
The size and height of the "pyramid of the Sun" are equally vague. The first news in 2005 mentioned sometimes 70 meters (article from Dnevni Avaz translated on the BBC website (en)), sometimes 100 meters, with a base of 220 x 220 m (AFP news published here (en)).
If one looks at the "official" source, the Foundation website, there is again this figure of 220 meters, but this time it is for the height of the pyramid! This figure is found in a press release (bs) of 2006, February 25th, on the Bosnian part of the website (with the title "Jedanaest dokaza o postanjanju bosanskih piramida", "Eleven proofs of the existence of the Bosnian pyramids"): "The pyramid of the Sun is 220 m high, that is a third more than the pyramid of Kheops in Egypt". Nowhere is explained how this height has been calculated, nor how the precise altitude of the pyramid base could be determined (a look at the contour lines on the topographic map shows a difference in altitude of at least 250 m between Visocica top and the level of the valley...).
A single other figure is given by the Foundation website about the size of the pyramid, in the already quoted document, "Scientific arguments" (bs)  from May 2006. There, again in the paragraph "Perfect geometry", one can learn that the "precise measurements" made by the Institute of Geodesy of Sarajevo are, for the North face of the pyramid, "an equilateral triangle, with sides of 365 m and angles of 60°". A few comments on these "precise measurements" by this strange Institute of Geodesy:
– If this is correct, as it is elsewhere often said that at least three of the four faces of the pyramid are identical, the base of the pyramid should be a square with sides of 365 m; a simple calculation then shows that the height of the pyramid should equal the half-diagonal of this square, about 257 m, but this figure is again different from every other given by the Foundation.
– There is again the question of the exact altitude of the base of the pyramid (not to mention the exact place of the angles): for a measurement with a precision of one meter, they had to know exactly where is this base; but these measurements have been made before the beginning of the excavations (and the present excavations, in 2006, take place mostly at mid-height of the pyramid), and, even if there were a pyramid, nobody presently can have the slightest idea of the exact altitude of its base - which could be buried under thick alluvial deposit, or on the contrary be raised on a natural height.
– Last, this figure of 365 meters seems to me quite funny: why choose this figure, when it is, as said above, impossible to make a measurement with a precision of one, or even a few meters? Is it because someone hoped to impress the public? If so, it was a success, as some people, on forums devoted to the archaeological "mysteries", immediately proclaimed (en) that there was an evident link with the number of days in a year, and therefore with the "sacred geometry" of the pyramids. It’s no use to try to explain these people that the metric system (en) was invented a very long time after the supposed building of the pyramid, they will answer that this metric system is itself derived from natural properties of the Earth, so that it is not surprising that it was used by the pyramid builders and/or the Atlanteans... What is more, Mr. Osmanagic himself suggests this link, when he says in a article published on 2006 April 17th in Avaz: "The North face of the pyramid of the Sun is an equilateral triangle which sides are 365 m, and that symbolically corresponds to the number of days in a year"...
There is a last amusing peculiarity in the document "Scientific arguments": the document uses a picture (picture 7), given by the Institute of Geodesy of Bosnia and Herzegovina, proving, according to the author, the existence of "regular terraces" on Visocica - which is therefore a "step pyramid". The attentive reader will however notice that all the slopes visible on this picture show the same pattern of terraces; that is not surprising, as this picture is in fact a 3D view constructed discontinuously from the contour lines (that means that there was no attempt to "smooth" the slopes, the relief is constructed in sucessive "slices", each corresponding to an interval between two contour lines); the next picture shows the same view, but this time after a "smoothing" of the slopes, and then, no more terraces!