I had to poke around to find this: "Before the experiment, 18 high-performance pumps make sure that the drop tube is almost free of air containing only one ten thousandth of the normal air pressure. Due to the vacuum, the air resistance is so low that the Bremen Drop Tower can provide one of the best quality of microgravity - in some aspects even better than on the International Space Station (ISS)"
The longest vertical shaft you're likely to find is around 3km, which gives you a little over 20 seconds of freefall and a couple seconds of violent deceleration.
But the problem is, you're dealing with acceleration squared. The Bremen tower already does almost half that time (9.3s with the slingshot), so it's probably not a big enough difference to warrant the effort and travel.
Woa, does anyone know in what way this tower provides less gravity than the space station?
The station is likely better in terms of gravity, but in terms of test conditions, you're somewhat limited by the astronauts being there.
In the microgravity tower, translations within the experimental container will not result in divergent trajectories, so no drift will occur.