There are many things which completely circle the globe. The
first thing that comes to mind is the equator, but the artic and
Antarctic circles also circle the globe (as well as every other
degree of latitude).
The taiga forest circles the globe.
The atmosphere circles the globe.
yes the imaginary line is the equator and it circles the globeat
its widest point.
Latitude and longitude lines.
the 'boobie-sucker' line