Velara III is a planet located near the Pleiades Cluster.
In the mid-24th century, the Federation's Terraform Command established the Velara Base on Velara III after designating the planet for terraforming, phases II and III of which were a 35-year effort.
The terraforming was, however, canceled in 2364, when it was discovered that the terraforming was killing silicon-based lifeforms in a thin layer of water between two planetary layers, dubbed as "Microbrains".
Following the discovery of the Microbrains, and the retaliatory death of Hydraulics Specialist Arthur Malencon by the Microbrains, an agreement between the little crystals and Captain Picard of the USS Enterprise-D placed Velara III under a 300-year quarantine. (TNG: "Home Soil")