The pre-Columbian city of Guayabo is located 19 km north from the town of Turrialba, province of Cartago, on a high plateau at 1,100m of altitude, on the skirts of the Turrialba volcano; the area has an average temperature of 20° and 82% humidity, the yearly average precipitation goes from 3,500 to 4,000 mm.

The 20 hectares settlement is believed to have been occupied between 1000 B.C. and A.D. 1400, after which its inhabitants vanished. It is unclear why the ceremonial and political centre was abandoned, the Spanish Conquistadors did not leave any record as to whether they found the ruins.

In July 2009, the ancient city of Guayabo was named an International Historic Civil Engineering Landmark by the ASCE (American Society of Civil Engineers.)

Some of Guayabo's pre-Columbian early civil engineering achievements are:

• The main water supply system which is still functioning: it collects water from nearby springs and transports it through open and underground channels.
• The cobblestone roads or “calzadas” (as called in Spanish) that lead to the entrance of the ceremonial centre and that stretch several km.
• The stone-paved roadways that lead to the different buildings from the monument. They were built with the necessary retaining walls to maintain the gradient and the structure.
• The stone was used to develop a system of pavements and walls that prevents erosion and mud slides.

Guayabo#1-diorama of the settlementThe settlement has a strategic location, it is near 2 rivers: the Lajas to the north and the Guayabo to the south and it follows an east to west line between the Turrialba volcano and the mountains of Talamanca. The political, religious and commercial centre is believed to have peaked round A.D. 800, when the main stone constructions were built.

As mentioned before, when the settlers arrived to the area, in the early 1800's, they had no idea of what was buried under the tropical forest. In 1850 the ancient city of Guayabo was part of a cattle farm. The first pre-Columbian artefacts were dug out by the owners when they started felling down the trees to turn the land into cow pasture. Unfortunately that is when the looting also started.

Guayabo#2-view from aboveIn 1892 Prof. Anastasio Alfaro, a researcher from the Costa Rican National Museum is invited by the owner of the property, Mr. José Ramón Rojas, to investigate the area. He finds several stone tombs, pieces of ceramic, and tools, believing they have discovered an indigenous cemetery.

It is not until 1968 when Mr. Carlos Aguilar Piedra, an archeologist from the UCR (Universidad de Costa Rica, main Costa Rican state university) discovers the mounds - stone foundations on top of which were built the thatched huts - that he realises it is a settlement instead.

In August 13th 1973 Guayabo is declared a National Monument; at the time the protected area was comprised of 65 ha. In 1980 it is expanded to a total area of 217,9 ha.

Guayabo #3 petroglyph-mapFrom the 20 ha, where the settlement is located, only 4 have currently been dug, the rest is still covered by vegetation. Nevertheless, thanks to some high resolution photos taken by NASA with the AIRSAR radar system in the spring of 2004 (1), it has been proved that those 4 ha are the centre of the settlement. Those photographs also showed that there are several cobblestone roads that stretch over 70 km from the settlement. Only 200 m of one of those roads have been cleared so far.

Those cobblestone roads were painstakingly built using human work labour. There were no pack animals to help! The river stones (lajas in Spanish) were probably hauled up the mountain one-by-one thrown over the backs of workers. Not only is that amazing, but it also proves the existence of a fairly complex political / religious system. Otherwise, how would you convince people to carry heavy rocks (some weighing close to 100 kg) uphill for several kilometres?

Guayabo inhabitants left behind several petroglyphs whose meaning is still not well understood. One of the most famous looks like a spiral (see picture #3) and it is believed to be some sort of map of the settlement. There is a theory from an amateur archeologist - Michael O'Really - that suggests that it might be some sort of calendar, although nobody has proved or disproved it.

Guayabo#4 monolith-alligator sideThere is also a monolith that depicts a stylized version of an alligator on one side and an upside-down jaguar on the other (see picture #4); it is wedge-shaped and buried 1 metre deep into the ground, to anchor it. It is approximately 1600 years old, carved by two different artists (the technique is noticeably different) and believed to represent the fact that Guayabo was some sort of cultural and religious bridge between northern and southern pre-Columbian civilizations.

It is important to point out that although Guayabo is probably the best known archeological site of Costa Rica it is not the only one: there are several that are currently being excavated and studied. For instance, 25 km east- in a straight line - from Guayabo is Las Mercedes a very similar but not so impressive pre-Columbian settlement; it is believed to have competed politically and commercially with Guayabo.

For more pictures of Guayabo, please click here.

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(1) Thanks to a grant from the NSF (National Science Fundation), NASA deployed their Airborne SAR (AIRSAR) radar system in southern Mesoamerica and Central America in the spring of 2004. The radar signals of AIRSAR - long wavelength and low frequency signals- easily penetrate through forest canopy. This techology is extremely useful for archaeological applications in tropical environments.