Simplify - square root of 4^4

$- \sqrt{4^{4}}$

Raise $4$ to the power of $4$ .

$- \sqrt{256}$

Rewrite $256$ as $16^{2}$ .

$- \sqrt{16^{2}}$

Pull terms out from under the radical, assuming positive real numbers.

$- 1 \cdot 16$

Multiply $- 1$ by $16$ .

$- 16$