Archeology is often a thankless task in the Netherlands, where the rain and a scarcity of stone for building mean that most traces of ancient life have washed away.
So the discovery of the foundations of a wooden watchtower, built by Roman soldiers on the banks of the Rhine nearly 2,000 years ago, has Dutch archeologists beside themselves with excitement.
They say the watchtower was part of a chain of observation posts guarding the river, which marked the border of the Roman empire at its greatest extent.
The chief archeologist on the project, Erik Graafstal, thinks that the towers were used to monitor shipping on the river and to sound the alarm if hostile Germanic tribes threatened to attack.
While most wooden structures crumble with time, the watchtower's foundation survived because it was buried under a Roman road built about a century later.
With the discovery of the well-preserved foundation about 22 miles southeast of Amsterdam, other fragmentary remains also can definitely be said to have been watchtowers, Graafstal said.
The towers were built at intervals of 500 to 1,500 meters (500 yards to a mile) -- close enough that guards would have been able to signal each other and alert soldiers stationed nearby to any trouble on the river.
Graafstal said the find rivals in importance the wreck of a fully loaded Roman freight ship that was found in the same area in 1997. It will be excavated this spring.
"The discovery of the watchtower is at least as nice because due to its exemplary preservation, we can get a lot of new insights into the appearance of this kind of building and the functioning of the border," Graafstal said.
The archeologists date the tower possibly as early as A.D. 50, in the reign of the Emperor Claudius.
Based on the size of the remaining corner poles, the tower would have been square, 10 feet on each side and about 16 feet high. It was surrounded by a low wall, a moat and sharpened wooden stakes.
Detachments of three or four soldiers would have been sent to the tower from the nearby army base, traces of which have also survived. Near the tower, archeologists found bones and other remains of food that the soldiers ate and such objects as a spear point, a coin, an ax, a sickle and an ancient pen.
Professor William Harris of Columbia University, a historian not associated with the Dutch dig, said the discovery fits well with the broader background of Roman history. He said soldiers manning the towers would likely have been a mix of Roman legionaries and auxiliary troops recruited from other frontier regions of the empire.
"The Romans first arrived in this general area in the times of Caesar," around 53 B.C., he said. "The Roman occupation was not heavy, but sufficient to keep order.... They used very functional wooden forts, which were put up and taken down according to need."
By Claudius' reign, A.D. 41-54, some stone structures similar to the Dutch tower were built along the German Rhine, Harris said. But only during the reign of Nero, in 54-68, did the Rhine become firmly fixed as the empire's northern border.
"It's not that they didn't think about pushing forward, but while Nero was in power, if you were a local governor, you didn't wage war because the emperor got jealous," Harris said. "If you were defeated, that was certainly bad, but victory was also bad."
The river was used for trading by both Romans and local Germanic tribes, known to the Romans as the "Batavi," and the observation posts may have played a role in ensuring that taxes were levied on passing boats.
The Dutch archeologists believe that the tower was destroyed in the late 60s, then rebuilt. Such a time frame would put the destruction during a revolt of the Batavi recorded by the Roman historian Tacitus.
Tacitus describes a clash between the Romans and Batavi in the Dutch countryside -- as wet and marshy then as it is now -- as "more a naval contest than a land battle."
"The Batavi leapt lightly through the shallows," wrote Tacitus, while the Romans, "struggling among the waters, exerting every limb where they found some firm footing, whether they could swim or not, were subject to one common destruction."
In the end, though, the Romans won.