The cavetto (also known as the hollow or cove) is the concave counterpart of the convex ovolo: both take the form of a quarter-circle arc. But where the projecting mass of the ovolo conveys sturdiness and loadbearing ability, the hollowed-out cavetto is used to express delicacy and lightness, in particular as a crowning moulding (shown above) for ‘topping off’ a building, allowing it to ‘feather out’ at its highest point.

The shadow gradient of the cavetto is the reverse of the ovolo, being darker at the top and lighter at the bottom. With the sun at 45°, the upper part of a downward-facing cavetto is about ½ shaded, transitioning smoothly to fully lit at the bottom. The thin, fully-lit fillet that sits on the cavetto in the crowning moulding contrasts with the shaded upper part to bring a sharp definition to the feathered edge of the building.

Whether facing down or up, the cavetto also provides a simple and elegant way of transitioning from a vertical to a horizontal surface; it is still commonly seen in this role, as a plaster cornice covering the joint between wall and ceiling in many contemporary houses.