Over three thousand years ago, in the fertile jungles of lowland Mexico, the first civilisation in the Americas was born. Five hundred years before Rome was founded, the Olmec were building great cities with pyramids and ball courts. Considered by most archaeologists to be the 'mother culture' of Mexico, the roots of the later Maya and Aztec cultures lie with the Olmec. One of the most extraordinary feats of the ancient Olmec was their monumental sculptures. The inhabitants of the site of La Venta erected huge sculptures, some of which weighed up to 40 tonnes. The most famous of these are the massive stone heads. Believed to be portraits of their leaders, they are over two metres high and sculpted entirely without the help of metal tools. There are thousands of tonnes of stones at the site but, most extraordinarily of all, these sculptures are found in an area where there is no rock available. The area identified as the source of the Olmec boulders lies in the Tuxtla mountains over 160 kilometres away. And between these mountains and La Venta the land is criss-crossed with massive rivers and swamps which would have made the transportation even more difficult. So how did the stones get to La Venta? Archaeologist Ponciano Ortiz believes the Olmec would have transported their stones by water wherever possible. But Anne Cyphers, who has excavated and moved large stone monuments at another Olmec site - San Lorenzo - is convinced that the stones would have been moved over land on sledges during the dry season using the simplest technology. Engineer Peter Guthrie and rigger Bob Loew soon encounter the difficulties of moving a 12 tonne stone over land and on water with the most basic technology. Peter falls ill and cannot go to Mexico so Bob struggles on alone with Peter's preliminary sketches. Getting the stone on the sled and moving it over land proves far more difficult than expected but when Bob tries to manoeuvre the stone onto a massive raft and float it out into the lagoon he realises just what he's taken on. But once they got the stones to the site, how on earth did the Olmec produce such stunning sculptures using only stone tools? Glynn Williams, professor of sculpture at the Royal College of Art, doggedly struggles to carve a stone head using only the stone tools that would have been available. He finishes with an even greater respect for the master sculptors of the Olmec.