Palaven

"The only thing on this planet that isn't silver are the turians. It's all too clear they're made of steel." - Admiral Jon Grissom, Human Systems AlliancePalaven is the third planet from the star Trebia and the homeworld of the turian species. From its capital, Cipritine, it is the seat of an expansive and highly militarised space faring empire which dominates the majority of Inner Council Space. Second only to the Citadel, to which is swears political obeisance, Palaven is the most heavily defended population centre in all the Milky Way. It has only been threatened twice in recorded history; once in 710 CE, at the height of the Krogan Rebellions, and twice during the Reaper War of 2186 CE, when it was occupied for the first time in its history by invading Reaper forces. 
Turian civilisation on Palaven was established approximately 15,000 years ago, during the 13th millennium BCE - a time when humanity was still living in nomadic hunter-gatherer tribes during the Upper Paleolithic period. Its history and culture have been shaped by the turians' martial attitude, which permeates every aspect of Palaven's society, from architecture to art to politics. The visible fortifications of turian cities reflect their martial society, but since joining the galactic community, internal conflicts have become honour-bound affairs with few casualties among noncombatants.
Unlike most other habitable worlds, Palaven has a metal-poor core which generates a weak magnetic field and allows more solar radiation into the atmosphere. To combat this increased level of solar radiation, most forms of life on Palaven, including the turians themselves, have evolved some form of metallic 'exoskeleton' containing thulium to protect themselves. Non-turian visitors are advised to wear enviro-suits or other radiation protection when visiting Palaven to avoid developing skin cancers and blinding eye diseases. Although life on Palaven is carbon-based and oxygen-breathing, it is built on dextro-amino acids, making it one of the rarest ecosystems in the galaxy.
Palaven's photosynthetic life is similarly impressive, shutting down vulnerable metabolic processes during daylight hours and repairing cellular damage at night. A large number of Palaven's plants are only active at night and utilise bioluminescence to attract pollinating insects, birds and large herbivores. This reliance on bioluminescence to facilitate propagation has caused a number of Palaven' species to evolve tetrachromatic vision, which allows them to perceive ultraviolet light. This includes the turians themselves, who have evolved to have UV-sensitive vision in response to their prey's own evolution.