We don't know for sure, and it's not clear that they are the same camp. It appears that Drusus' camp is the site at Oberaden, North Rhine-Westphalia, on the Lippe River. The odds-on bet for Aliso is the site at Haltern am See, downstream from Oberaden. Oberaden was a large enclosure, possible large enough for three legions in tents, established about 11 BC.

The site at Oberaden, and a smaller fort/port at Beckinghausen, seems to have been abandoned about the time Haltern was founded around 5 BC. The earliest occupation at Haltern was a two legion enclosure with no permanent structures. This was later rebuilt into a one legion fort with permanent housing, sewers, and other amenities. The Lippe was probably navigable year-round up to this point, making resupply by river boat possible, and a port existed near the fort. A lead ingot with the stamp "XIX" probably means Haltern was occupied by Legio XIX, one of the three legions lost at the Battle of the Teutoberg Forest.

Another fort, at Anreppen, east of Haltern along the Lippe, dates to about AD 4. Both Haltern and Anreppen were abandoned around AD 9.