The ornamental design for a vaultdome, as shown and described.
FIG. 1 is a perspective view of a vault dome showing my design.
FIG. 2 is a top plan view thereof.
FIG. 3 is an elevational view taken from one end thereof, the opposite end
being the same as the end shown.
FIG. 4 is an elevational view taken from one side thereof, the opposite
side being the same as the side shown; the interior of the dome being
unornamented.