As noted in THIS POSTING of 13 April 2003, there is a hairline from the north pole to the south pole on the 180° line.

Over water, it's a blackish blur, but over Russia and Antarctica, it is a distinct hairline.

This file shows the north and south hairlines and the two swaths where the line enters and leaves the Russian mainland. The swaths average 128 meters in width.

To see them,

Turn off Latitude - Longitude

Turn on "180° Lines"

Zoom in on either the north or south lines to below 10 kilometers altitude. Even better is less than 2 kilometers.

Turn off "180° Lines"