Rotunda feature (4)
I believe the answer is:
dome
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">rotunda feature</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for dome that I've seen before include "Hemispherical structure" , "Old cathedral" , "description of church roof?" , "Curved roof" , "A stately building" .)