The lost city of the extinct Loque'eque, whose engineered virus turned members of an Enterprise landing party into Loque'eque driven by an instinct to find it.
Urquat is the ancient home city of the Loque'eque, a species that died out long before Enterprise entered the Delphic Expanse. It appears in the third-season episode Extinction.
Facing sterility and extinction, the Loque'eque created a mutagenic virus that rewrites other humanoids into members of their species and gives them an urge to return to Urquat. In 2153 Archer, Reed and Sato are infected on the planet and transformed; T'Pol, whose Vulcan physiology resists the virus, stays with them as they make for the city.
They find only overgrown underground ruins. Phlox develops a cure while another species' containment team, which has burned out earlier outbreaks, demands that the infected be destroyed. Archer keeps a sample of the virus as the last trace of the Loque'eque.