The Enfield Tennis Academy is an elite sports academy that was founded by James O. Incandenza and is currently run by Charles Tavis. It one of the primary settings for the novel, alongside Ennet House, which it "happens to" overlook.
Important features of the E.T.A. are its hilltop location and its complex system of underground tunnels. In fact, the entirety of the E.T.A. is "traversable by tunnel" (51), something that Avril Incandenza uses to her advantage, as she refuses to go outside. Throughout most of the novel, Hal Incandenza smokes marijuana in the secrecy of the tunnels. Another feature of the E.T.A. is the "Lung," an "inflatable dendriurethane dome . . . that covers the middle row of courts for the winter indoor season" (51) and is stored in a tunnel that is impassable from March to November.
The "lung" is a classic example of something Wallace does often in his work: ascribe bodily characteristics to man-made spaces that people operate in. Other examples include
- In The Broom of the System, the telephone switchboard has a human temperature of 98.6˚ and the character LaVache refers to his own personal phone as his "lymph node" (214).
- In Infinite Jest, the WYYY engineer pumps “the coaxial medulla” through “into the crawlspaces above the high false ceiling of the corpus callosum’s idle tennis courts” (183). The corpus callosum makes it the "brain" of the M.I.T. student center, and furthermore, the coaxial medulla is reminiscent of the “annular process or protuberance (in the brain) [which is] the Pons Varolii; ‘a process of the medulla oblongata; thus called by Dr. Willis  in regard it surrounds the same, much like a ring.’ Chambers Cycl. 1727-51.”
One of E.T.A's primary goals is to keep its athletes as insulated as possible. This is for their own benefit, as some of these kids who go on to play in professional leagues (which is referred "The Show") end up psychologically breaking down from the pressure.
There is a Big Buddy System at E.T.A., which consists of each player in the 18-and-Unders keeping "his more experienced wing over" four to six 14-and-Unders. The dialogues between Big and Little Buddies reveal a good deal about some of the older E.T.A. students.