What it was before we cannot know. It is said very clearly.
Now it serves as a radio station. Or, rather, soon will serve:
> І сёння к вежы прывязалі
> драты ўстрывожаную даль...
> О, прадзеды, каб вы пазналі
> антэны стынучую сталь!
>
> Today they bound to the tower
> the wires of disturbed distance.
> O Ancestors, if you only could see
> a cold steel of an antenna.
(sorry for a sloppy translation). This pretty much implies that the men in boots are workers.