A hard-hat tour on Thursday of the galleries currently under renovation at the Wadsworth Atheneum Museum of Art in Hartford showed a lot of what one would expect at a hard-hat tour — ladders, primered walls, workmen with power tools — and one fun surprise.

On one wall of what was once the management office of the Amistad Center for Art & Culture in the second-floor Colt mezzanine area is a room-wide, three-primary-color mural by Sol LeWitt. "Wall Drawing #352" has been there since 1980.

Employees have always known about the mural. They put their office furniture in front of it and sat there every day. But the area has been off-limits to the public for 15 years.