In 1985, German archaeologists discovered a Roman legionary base from the reign of Augustus east of the German town Marktbreit am Main. What was unusual, was that the fortress had never been used. It was probably built for two legions that were to attack the kingdom of Maroboduus, the leader of the Marcomanni, in Bohemia. This military operation was to take place in 5 CE, but an insurrection in Pannonia prevented its execution and the base at Marktbreit was abandoned. Some photos (not very spectacular) are here; the satellite photo is not very helpful either.
Marktbreit am Main