While Rome's legions swept across Iberia like a plague of metal and fire, a small community of indigenous tribes in Northern Spain repelled the Roman armies for about 200 years - the longest defense ever sustained against the mighty Empire. One of the main Celtiberian strongholds was the city of Tiermes. It housed about 4,000 members of the Arevaco tribe at one time, but fell to the general Titus Didius in the year 98 B.C. Expelled to the lower lands away from the acropolis of Tiermes, the original Termestinos might have faded into history's shadow. But the Romans who moved into Tiermes to construct their aqueducts, temples, theaters, and roads didn't destroy the original infrastructure as in the majority of the similar cases archaeologists have uncovered. Yes, the Romans built over the existing structures, but in many cases used the Celtiberian foundations and simply improved on them. Why this unique change in custom? Tiermes boasts one of the most extensive and well-preserved style of rock architecture from the Roman era, called "arquitectura rupestre" in Spanish. One Spanish archaeologist has called Tiermes "the Spanish Petra." Ancient architects carved the foundations of the buildings from the bedrock and supported the higher levels of the houses with wooden beams. These beams no longer exist but the holes in the walls that held up the second and third floors still do. Some rock faces reveal what used to be seven-story housing complexes. The aqueduct, the life force of any Roman city, doesn't reach to the sky like its brothers in Segovia and Tarragona. The two branches of Tiermes's waterway were also carved from the bedrock. Engineers, using tools not unlike the modern level and theodolite, calculated the exact angle of the rock-tunnel's floor to keep the flow moving 24 hours a day. One branch feeds into a subterranean gallery that then flows into the largest house excavated at Tiermes, La Casa del Acueducto. Belonging to most likely the wealthiest family in town, this house provided archaeologists with colorful mosaics, rich paintings and enough artifacts to fill half the storage facility. The other branch of the aqueduct flows from one of the city's four gates up to the acropolis, where it passes through the heart of the forum, servicing the fountains and the baths. Only one corner of the bath complex remains standing – a thick brick column that resembles a large T. In addition, about six major highways crossed through Tiermes, some of Celtiberian origin, some of Roman limestone and others of the bedrock, carved into passable roads. The famous medieval knight El Cid supposedly used one of them on his adventures to re-conquer Spain from the Moors. Since modern excavation began in 1975, only about 3% of the entire city has been excavated. The Celtiberian necropolis has been found, but not the Roman one. One small temple lies in the forum, but for a city that large another one must be close by. Perhaps its ruins sit underneath the 12th-century hermitage near the ruins, where 200 medieval burials were found? Christians often rebuilt their churches over pagan holy sites. Another debate revolves around the large area that only a few years ago was thought to be the main water distribution building for the city. Now scholars believe it could be the city's main plaza, judging from the dozens of column bases discovered around the area. We'll be digging nearby. >Continue>