The surface of Betazed near Lake El'nar
Lake El'nar was a large stretch of water on the planet Betazed.
As children, Deanna and Kestra Troi lived near Lake El'nar with their Betazoid mother, Lwaxana, and Human father, Ian Andrew.
Kestra later drowned in Lake El'nar when Deanna was still a baby.
In 2370, Deanna Troi visited a recreation of Lake El'nar inside her mother's mind while attempting to figure out why Lwaxana was so distressed. (TNG: "Dark Page")
According to the Star Trek: The Next Generation Companion, Lake El'nar was named for a friend of episode writer Hilary J. Bader.
According to the script, El'nar was pronounced as "el-NAR".