Although, towns are considered at 20m elevation for spotting and LOS purposes:
8.42 Town Hexes.
When spotting from a town hex or tracing LOS through it, treat the town hex as being 20 meters higher than the terrain it sits on. So, if a town is located in a hex on a 20 meter elevation line, then treat it as 40 meters in elevation for purposes of LOS and spotting range. A town at zero elevation counts as 20 meters in elevation.