What is the atlas?

In anatomy, the atlas (C1) is the most superior (first) cervical vertebra of the spine. The atlas is the topmost vertebra and with the axis forms the joint connecting the skull and spine. The atlas and axis are specialized to allow a greater range of motion than normal vertebrae. They are responsible for the nodding and rotation movements of the head. The atlanto-occipital joint allows the head to nod up and down on the vertebral column. The dens acts as a pivot that allows the atlas and attached head to rotate on the axis, side to side. The atlas's chief peculiarity is that it has no body. It is ring-like and consists of an anterior and a posterior arch and two lateral masses. The atlas and axis are important neurologically because the brain stem extends down to the axis.

Where is the name coming from?

It is named for the Atlas of Greek mythology, because it supports the globe of the head.

Where is it located?

In the image on the right side you see the location of the atlas as orange dot at the top of the spine. In real life the atlas itself is a pretty complex looking bone.