This picture of a Brazilian sky by Alex Baguio starts our readers' gallery focusing on the theme of sky.
Jami Bolton: "The sky in San Vincenzo, Italy, as a storm is blowing in off of the coast. Taken while on holiday."
David Heinersdorff: "The three spires of the Grand Palace and Jade Buddha Temple in Bangkok stand out nicely against fluffy clouds and a blue sky."
Alex Goffe: "The tops of skyscrapers in Shinjuku, Tokyo, disappear into the evening fog. Taken outside Shinjuku station's west entrance."
William Bradley: "This is taken from the Arctic Circle in Norway during a charity challenge. These were some of the first clouds we saw in days."
Sarah Sheldon: "An amazing colour sunset taken from a boat on a river near Damai in Borneo."
Martin Nijs: "A picture of the dome at Hiroshima."
Marion Glover: "Shade closing in on sunshine in Mexico."
Marina Elliott: "This photo was taken from our sailboat as we were anchored off one of the Gulf Islands, near Vancouver, Canada."