The opening of Glasgow School of Art's new building earlier this month was a celebration of art, creativity and education, but it was also a celebration of architecture.

The £30m building was designed by the US architect Steven Holl and sits opposite the school's main building designed by Glasgow's greatest architect Charles Rennie Mackintosh. Together, the two buildings represent what adventurous design can achieve.

Which makes it all the more disappointing that just a few minutes' walk from the School of Art, the future of another example of Rennie Mackintosh's work remains uncertain. Today, a fireplace designed by the great man in the Willow Tea Rooms has gone on display once again after being covered up for 20 years. But the building itself is up for sale and requires renovation and repairs getting on for half-a-million pounds.

The hope is that someone who values Rennie Mackintosh's work will buy the building to secure its future. The tea rooms represented a great advance in the architect's career but they are also of economic importance to Glasgow. The city would be worse off without one of Rennie Mackintosh's finest achievements.