What is the largest three digit number that has both vertical and horizontal symmetry?

A number with vertical symmetry will look the same when reflected across a vertical line through the middle. A number with horizontal symmetry will look the same when reflected across a horizontal line through the middle.

To have both vertical and horizontal symmetry, the digits must be the same when rotated 180 degrees. The only digits that work are 0, 1, and 8.

The largest three-digit number using only 0, 1, and 8 is 818. 818 has both vertical and horizontal symmetry.

Therefore, the largest three-digit number that has both vertical and horizontal symmetry is $\boxed{818}$.