Mars: Hellas Planitia. The largest visible impact crater in the Solar System is Hellas Planitia on Mars, a giant depression with a floor over seven kilometres (4.3 miles) below the Martian surface.
Dimensions. The recommended size for one parakeet is 25 inches tall and 25 inches deep. To house two birds comfortably, you should double that cage size to make it at least 50 inches tall and 50 inches deep.If you can afford it and have enough space, opt for a bigger cage.all cages work best for parakeets. This type of bird really likes to fly around and hop from place to place. If you can, choose a cage that exceeds the height recommendation of 50 inches.
p.s. to reproduce cockatiels and parakeets interior an identical section, the cage might neeed to be huge... room sized! Your birds can see colors, and they may also be able to see into the ultraviolet spectrum, well beyond the range of human color vision. This is a developing field of study, but scientists have found that birds like budgies and cockatiels have a wider range of color vision than birds like crows. Source(s): http://mbe.oxfordjournals.org/cgi/conten...