On that day, a total solar eclipse will sweep across the Northern Hemisphere, traveling from Russia to Spain while passing over parts of Greenland, Iceland and Portugal.

For the first time in more than a century, a total solar eclipse is coming to mainland Spain.

If you're fortunate enough to be inside the 180-mile-wide (290 kilometers) path of totality — the path of the dark shadow of the moon — in eastern Greenland, western Iceland or northeastern Spain, you...