A postbox in Cardiff is one of four across the UK to be painted black as part of Black History Month in October.
Royal Mail said that each postbox - in Wales, England, Scotland and Northern Ireland - has been painted black with a gold trim to honour black Britons, both past and present.
Each of the special edition postboxes features a significant figure in the British black community, as well as a social media link so people can learn more.
The Cardiff postbox, on King Edward VII Avenue, features pioneering nurse and businesswoman Mary Seacole.
Seacole nursed wounded British soldiers back to health during the Crimean War (1853-1856) and built a dedicated place for them to recuperate, known as the British Hotel.
She featured on a set of stamps released in 2006 to celebrate the 150th anniversary of the National Portrait Gallery.
The Royal Mail said this postbox was chosen for its proximity to Cardiff City Hall and its central location within the city.
Peter De Norville, Royal Mail's head of diversity and inclusion, said: "Black History Month is a great opportunity to celebrate the contributions that black people have made to this country over many generations.
"We are also using it as an opportunity to celebrate the vital work that our black employees do throughout the nation, from the mail bag to the meeting room."
A QR code on the postboxes can be scanned to bring up a full list of black Britons who have appeared on special stamps over the years.
The other three postboxes are in London, Glasgow and Belfast.
The London postbox is in Acre Lane in Brixton, which is near to Black Cultural Archives - a leading museum for the British black community.
This box features the image 'Queuing at the RA' by Yinka Shonibare CBE - one of six artists commissioned by Royal Mail to produce original artworks for a set of special stamps issued to mark the 250th anniversary of the Royal Academy (RA).
Mr Shonibare said: "As a citizen of the commonwealth, it was particularly important to me to be making a visible contribution in a historic public space."
Footballer Walter Tull, who become the first black player for Rangers, appears on the Glasgow postbox in Byres Road.
He featured in a set of stamps released in 2018 to mark the centenary of the end of the First World War, and was also the first black Army officer to command troops in a regular unit. He was killed in action during the war.
Sir Lenny Henry CBE, the stand-up comedian, actor, singer, writer and television presenter and co-founder of the Comic Relief charity, is honoured by the postbox in Bedford Street, Belfast.