Silvereyes is, at the time of Ringworld (in 2851 at least), the furthest Human world from Earth (21.3 light-years, 60 days at Quantum-I hyperdrive speeds), orbiting Beta Hydri. In Niven's obscure story The Color of Sunfire it has entire continents covered with Slaver sunflowers (bred as defense for Thrint manors, they focus sunlight using silver leaves as parabolic reflectors), giving it an appearance from orbit of having "silver eyes". The Man-Kzin Wars books, conversely, have it entirely covered by a world ocean, with groves of sunflowers growing up from the bottom of the ocean. The Ringworld Roleplaying Game describes it as an ocean planet dotted with island shield volcanoes. It seem that people in fact know very little about the planet.

Sources and references: The Color of Sunfire, Ringworld RPG, Ringworld,

Other sites: Known Space Concordance, Larry Niven Wikia,