The Tower of London, viewed from the River Thames with the Union Jack.
I was frustrated that I can't find information about this stamp on the Royal Mail website. Apparently, this was issued by the Universal Mail United Kingdom, the postal service in the UK aimed at the tourist market. This stamp was part of the Historic Royal Palaces Booklet issued in June 2011.
Palacio Episcopal de Astorga
It was designed by the Catalan architect, Antoni Gaudí, one of his three works outside Catalonia.
The palace is now a museum of religious art, called Museo de los Caminos.
The stamp was released on 17 July 2012.
Two castle overlooking the Werra valley.
The two castles are the Ludwig stone castle in Hesse and the ruins of Hanstein in Thuringia.
The view of the two castles is symbolic of overcoming the division of Germany.
The stamp was issue on 3 February 2011.