The remains of a wooden bridge built over 2,000 years ago have been discovered in Aegerten, Switzerland. More than 300 oak piles from the bridge spans over the Zihl river were unearthed, preserved in the waterlogged soil of the silted-over riverbed.Archaeologists had found remains of Roman military structures on both banks of the Zihl 40 years ago, so when construction was planned in the same area, a team from the Archaeological Service of the Canton of Bern excavated the site. They took samples of the oak piles, removed some of the pointed tips of the posts, and examined them in the laboratory.Dendrochronological analysis found that the bridge spans had been repaired or rebuilt numerous times, with the earliest structure dating to around 40 B.C., the earliest years of the Roman conquest of Switzerland after its defeat of the Helvetii tribe. The most recent posts date to 369 A.D., a turbulent time when Emperor Valentinian added to the fortification of the Rhine Limes under pressure from Germanic incursions.Also known as the Thielle river, the Zihl was a busy transportation route in the Roman era. It was part of the Roman Jura transversal, the road that connected the Jura mountains to Augusta Raurica, the oldest Roman colony on the Rhine and capital of the Rauraci tribe 50 miles northeast of modern-day Aegerten.The bridge was located at a key intersection of the water routes and the road. It was at the gates of Petinesca, a small town and Roman service station that offered supplies and shelter to travelers on the road from Aventicum, capital of Helvetia, to the major legionary camp and associated civilian settlement of Vindonissa. An offshoot of the road branched at Petinesca, crossing the Jura through the mountain pass of Col de Pierre Pertuis and terminating at Augusta Raurica.With so much traffic on the small bridge, a great many artifacts were thrown or accidentally lost in the river. The excavation found numerous objects, including hobnails from human shoes, horseshoes, axes, a fishing trident, keys and coins. One particularly notable find was a large plane carved from a single block of wood with an iron blade insert. Both the wood and the blade are in excellent condition.