Although the geography of the area has changed in the millennia since the Olmec lived there, and the course of the Coatzacoalcos River has changed its course, sent Lorenzo would have originally stood on an island in its centre. With its high ridges, the island would have protected the city quite effectively from both floods and invasion. Generally, however, although some conflicts usually arise between multiple civilizations in the same area, there was no real evidence of battles or sieges.

The city itself underwent various incarnations over hundreds of years and with different groups of Olmec people. It even stood vacant for quite a while around 500 BCE. Some new buildings and a ball court were added in the later years, but nothing was done to maintain its former glory. Archaeologists found evidence of a main city structure, several nearby villages or clusters of farmer homes, and many statues and other artefacts. They even discovered evidence of aqueducts to transport fresh river water into the city's most high-class areas, to fill artificial pools, and the unique Monument 9, which is a well-shaped like a duck.

Since the Mesoamerican area is so hot and humid, no soft furnishings, leather, or other degradable items have ever been found. In San Lorenzo and the surrounding area, however, the stonework still stands as evidence of the grandeur of their civilization. Some was built with very large stones transported down the river from mines in the mountains, while others were constructed of carefully fitted smaller stones.