Wikipedia article claims those objects are sandstone. Sandstone is a kind of sedimentary rock typically showing layers such as these: https://en.wikipedia.org/wiki/Sandstone. However, no layers are found on the objects at Puma Punku of Tiwanaku, Bolivia. Concrete blocks show no natural layers. Four photos of the objects are shown below. They are marked for the features of concrete blocks, including flat and smooth surfaces meeting in 90 degrees, tiny round holes produced by air bubbles during concrete manufacturing, different textures on adjacent surfaces, etc. The highest resolution of the four photos cannot be shown here due to limited space here. They can be seen at
Object in the photo measures about 280 cm high and 360 cm wide. The whole object shows no sign of sedimentary layers typically found on sandstone. In the upper section are four red boxes and two green boxes that contain repetitive sculptures of two animals only. The sculpture surfaces are uniformly flat and smooth. The lower section shows flat and smooth surfaces with right angles. Red circles and red lines mark tiny round holes produced by air bubbles during formation of the concrete. Yellow and white annotations exist in the original image at
(Photo above) Red circle contains four levels of flat and smooth surfaces meeting in 90 degrees. Green and red arrows point to different adjacent textures. Two yellow arrows point to tiny round holes produced by air bubbles during concrete manufacturing. Image source:
(Photo above) At left are two red arrows pointing to flat and smooth surfaces with right angles. The second red arrow points to surface that is recessed deep into the object. Green arrow points to a different texture. Red box at right also contains flat and smooth surfaces with right angles and deep recesses. Two red circles contain tiny round holes produced by air bubbles during concrete manufacturing. Image source:
(Photo above) Four yellow boxes contain flat and smooth surfaces meeting in 90 degrees. Three red boxes contain tiny round holes produced by air bubbles during concrete manufacturing. At bottom are red and yellow arrows pointing to different textures on adjacent surfaces. Imagesource: