What were neanderthals like?

In construction, as our nearest genetic cousin homo sapiens neanderthalensis (occasionally classified as not a subspecies, but a new species homo neanderthalensis), the Neanderthals were extremely similar to our current species, home sapiens sapiens.

Body-wise, Neanderthals were virtually identical to modern humans, being just slightly shorter on average than contemporary humans of the time. They were a bit more stoutly built, having slightly thicker bones structures and anatomical arrangement, and analysis of their stature and bones have indicated that they carried a strong musculature, probably being 10-20% stronger than a comparable human. Contrary to popular belief, Neanderthals had at least an equal brain size as humans, with modern studies suggesting that adult Neanderthals actually had a slightly larger brain size.

A good breakdown of all the physical differences can be found on the Wikipedia link below.

Of course, we can't be sure what a living Neanderthal looked like, because fleshy parts have never been discovered (i.e. we've never found a mummified Neanderthal body). However, anthropologists think that they varied as much as humans in exterior looks.