The Spanish photographer Xavi Bou digitally combines sequential pictures of birds to create a single image, or chronophotograph, that reveals the shapes of their flight paths against Catalonian skies. His work shows the variety and beauty to be found in the daily activities of the local birds, including spiralling storks, swooping starlings and giddy swifts. Here: European herring gulls at Llobregat Delta. (Photo by Xavi Bou/Rex Features/Shutterstock)

Hong Kong art gallery director Sarah Greene said that Wolf, known for his work depicting mega-cities, has died Tuesday, April 24, 2019 night at his home. She said he was 64. Wolf won first prize in the World Press Photo competition in 2005 and 2010. Here: Architecture of Density #119, 2009. (Photo by Michael Wolf, courtesy of Flowers Gallery)

Members of the Michiana Rocketry prep a 10-foot, 450 pound porta-potty, mounted on rocket motors for launching, Saturday, December 6, 2014, from a field in Three Oaks, Mich. It made an arc and almost landed on a spectator’s pickup truck, 2,000 feet away. A group of Michiana Rocketry club members planned the project for more than two years. The club is trying to increase awareness of rocketry as a hobby and prove it’s possible to turn a porta-potty into a rocket and launch it successfully. About 30 people worked on the rocket, from engineers to sales people who lined up sponsors. (Photo by Don Campbell/AP Photo/The Herald-Palladium)

Located in the Mokattam Mountain in southeastern Cairo, Egypt, the Monastery of Saint Simon or the Cave Church is a beautiful and mystical location. The area is also known under the name of the “garbage city” because of the large population of garbage collectors or Zabbaleen that live here and who are the descendants of farmers who started migrating from Upper Egypt to Cairo in the 1940s.

MS Tûranor PlanetSolar, known under the project name PlanetSolar, is the largest solar-powered boat in the world The vessel was designed by LOMOcean Design, built by Knierim Yachtbau in Kiel, Germany, and launched on 31 March 2010. In May 2012, it became the first ever solar electric vehicle to circumnavigate the globe. The 31-meter boat is covered in over 500 square meters of solar panels rated 93 kW, which in turn connect to one of the two electric motors in each hull. There are 8.5 tons of lithium-ion batteries in the ship's two hulls. The boat's shape allows it to reach speeds of up to 14 knots. The hull was model tested in wind tunnels and was tank tested to determine its hydrodynamics and aerodynamics. The boat has been designed to be used as a luxury yacht after the record attempt is finished.

The sea otter (Enhydra lutris) is a marine mammal native to the coasts of the northern and eastern North Pacific Ocean. Adult sea otters typically weigh between 14 and 45 kg (31 and 99 lb), making them the heaviest members of the weasel family, but among the smallest marine mammals. Unlike most marine mammals, the sea otter's primary form of insulation is an exceptionally thick coat of fur, the densest in the animal kingdom. Although it can walk on land, the sea otter lives mostly in the ocean.