The Mostyn Art Gallery in Llandudno has been awarded the Gold Medal for Architecture, sponsored by the Design Commission for Wales in the UK.
The contemporary art gallery has been refurbished by Warrington-based Ellis Williams architects, who added two new galleries to the existing ones for £5.1m.
The Gold Medal is given in conjunction with the Royal Society of Architects in Wales, and is the only award supported by the Commission; the prize honours architects achieving the highest design standards.
The architecture judges recognised the Grade II-listed building for its natural lighting and the seamless fashion in which the gallery spaces are linked together, offering an ideal environment for the display of exhibits, as well as an enjoyable and uplifting space for visitors.
The judges also commended the new WISE building at the Centre for Alternative Technology at Machynlleth, designed by Pat Borer and David Lea, which was also shortlisted for the medal.
The award of the Gold Medal for Architecture follows a report published by the commission suggesting that the quality of design for the built environment in Wales is steadily improving.