Tower Communicator

The Garruw and the Humans had some difficulties in communicating. While it is possible to do so without external aid, it is rather difficult because of the size difference, vocal chord difference, and general lack of breathing the same air.
The towers were built in ages past so that a human could stand in one on one side, breathing their own air, and on the other side of the glass a garruw could stand and breathe their own air as well. No face concealing masks required.
The acoustics also allowed for the sound to carry well. A peculiarity of how they were designed cut out a lot of the underlying rumble of Grazu so that the humans could understand the words. Some context was lost, but the basic gist of the words remained the same.
There were a handful of towers found at the borders of Tholaren Dome, and a number of them found in the garruw city in Agarruta Drei, but since the two species haven't talked much in the interim years, the towers were converted into other buildings, for the most part. The only ones that remain as they are can be found on the plains between, built as relay stations between the two peoples.
The purpose was uncovered recently when it became necessary to converse with them once again.
A number of the towers have beautiful external windows made with a transparent material tough enough to withstand the force of the storms.
The original creation was a combination of garruw and human technology of the time.