This video - from viewer Mark Bloomfield - shows people gathering outside, as fire crews tackle the blaze on the National Library of Wales' roof.
It is thought that nobody will be allowed back inside the library until tomorrow.
Workers were all evacuated after the fire broke out.
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The Smith Commission is expected to set out new powers for the Scottish Parliament that could lead to major change for Wales
Remaining largely cloudy through the day with some intermittent drizzle likely in the east
Close interest is being paid in Wales to the recommendations of the Smith Commission for future devolution to Scotland