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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Still some showers around this evening but it will become drier with just an occasional shower.
A father-of-two was murdered by three men in a vicious attack as a result of a drugs turf war, a court has heard.
Plaid Cymru kicked off its election campaign today with leader Leanne Wood vowing to defend Wales in Brexit negotiations.