It is the detail that is hard to take in when you see it. The tracks climb the wall in orderly lines, as if the animals had walked up a façade, and the explanation lies not in biology but in geology.
01 What exactly you see
The surface is part of a working limestone quarry, and that is the key to the find: it was the extraction work that exposed the layer with the tracks, in the 1990s.
Counts vary by source, but more than five thousand identified footprints are cited, belonging to several groups: sauropods with enormous rounded feet, three-toed theropods, and other armoured animals.
They are dated to around sixty-eight million years ago, that is, the end of the Cretaceous, very shortly before the extinction that ended these animals.
02 Why it is standing upright
The process is the same one that raised the Andes. The mud where the footprints were left was the edge of a lake or a floodplain, perfectly horizontal, which later hardened into rock.
Millions of years later, the plate collision that formed the range folded and tilted those strata until they stood almost vertical. The mud surface that had been ground became a wall, with the tracks intact on it.
That is why the site reads so counter-intuitively: what looks like a climb is actually a walk, and the rows rising diagonally are the paths of animals moving over flat ground.
03 How it is visited
Access is organised from a park opposite, with viewpoints and a telescope platform, because the wall is still part of an active quarry and you cannot walk freely at its base.
There are guided visits that get closer, at set times and with helmets. It is worth checking the timetable before going up, because from a distance you can see the footprints but you cannot read them.
Light matters too. In mid-morning and mid-afternoon the sun comes in from the side and the marks gain relief; at midday, with vertical light, the wall flattens and it is hard to make anything out.
04 Why this site matters
What is exceptional is not that there are tracks: there are tracks in many parts of the world. What is exceptional is the concentration and the continuity, with very long trackways that let you follow the same animal for hundreds of metres.
That turns the wall into a document of behaviour and not only of anatomy. You can estimate how fast they were moving, whether they walked in groups, whether a young animal followed an adult.
And there is a real threat worth knowing about: the same activity that exposed the site puts it at risk, and parts of the face have fallen away with the rains. What you see today is not guaranteed for ever.
05 What you understand afterwards
After seeing it, the landscape around the city reads differently. The hills of tilted strata visible from any viewpoint stop being a postcard and become what they are: layers of sediment stood on end.
And the scale of the trip changes too. You are in a colonial city from 1538, considered old, five kilometres from a surface that records one particular morning sixty-eight million years ago.
