Real windows have curves. Real eyebrow windows, that is. These windows are a quirky way to let some light in, and even ventilate a top-floor space, all while adding a distinguishing element to a home’s appearance.

Eyebrow windows date back to the second half of the 19th century, where they appeared on medieval cottages with thatch roofs. An architect named Henry Hobson Richardson, the father of the Shingle style, brought them to popularity. Then, they were long, narrow slits with short windows on large, expansive roofs.

Today, eyebrow windows have become much more versatile. They’re found on everything from Post-Modern beach homes to converted garages used as guest houses. They must be custom-fit and many require a custom-made sash, but can be designed in any shape or size you desire.

While there are less expensive and less laborious ways to bring in light and ventilation to a top-floor space, few are as eccentric as the eyebrow window. They truly bring curves to a whole new level.