The Pentagon shopping concourse is unique mysteriouss surprising.

Your typical suburban mall it's not, no glaring lights, nothing modern. Character it has: You can watch televisions up near the ceiling, sample an exquisite pastry from the centrally located bake shop, buy a gun through a bulletin board ad, meet a WAC in the friendly pharmacy, sit in a chair and watch your Armed Services go marching by, try to decipher all sorts of arcant information that's posted about (such as what the Inner Orifice, FSN 1025-802-2470 is).

You can't miss the place. You're in it before you can bet lost in the 17 1/2 miles of Pentagon corridor. The Metro takes you right there, disgorges you up an escalator to a still-subterranean world of unexpected delights and curiosities.

Military Air

At one dark end of the sprawling concourse, there's a reminder of a boondoggle the government would prefer to forget. On two poles are silver signs with black letting that say: "Patients will remain in area for 30 minutes after receiving flu injection."

Nearby, there's a sign on room 2-D-167, the men's room. "This rest room will be closed daily for cleaning, 11:40 a.m. to 2 p.m." . . . There's a television set near the concourse a ceiling. The President is on, holding a news conference. Part of the reason may be because everybody's getting a haircut. At least 14 barbers are cutting hair and there's a crowd waiting.

Alert: A college course being offered has changed to a new classroom. Here are the directions: 1. Go to the first floor, corridor E Ring.2. Take stairway No. 64 to basement. 3. Go right to double doors (on left). 4. Go through doors and up the stairs (on right).

You can also sign up for Project 4250; Transcendental Meditation. "TM Management, Improvement Program for the U.S. Department of Defense offers the chance to: increase orderliness of thinking, enhance problem solving capabilities, increse productivity, increase intellgence (sic) growth rate, broaden comprehension and ability to locus."

There's a television set at the other end of the concourse. The President is on. Nobody is watching. The Tepee

A somewhat historic event occurred on the concourse yesterday: the "grand opening" fo an American Indian arts and crafts shop, known as "the Tepee" and owned by Deloris Abeita. Abeita said he is a full-blooded Pucblo who came to Washington three years ago from Isleta Pucblo. N.M. a reservation near Albuquerque.

"An Indian being here, it's a first," exclaimed a happy Paul Roessler, chief of the division of Indian Business enterprise. Bureau of Indian Affairs. Department of the Interior.

Well, almost a first, added Roessler, who is a Navajo."When our chiefs, different tribes used to come here," meaning Washington, he said, "it was to settle matters. Now it is to open business." He stood by proudly as a wide, red ribbon was cut, noting that his office wanted an Indian in business at the Pentagon and contacted "several" possible owners.

"The Indians," he continued, "were really the first in contact with the military. The first confrontation, actually. And referring to the shop's owner," she's from that area of the West where the cavalry was highly involved," though in an "unpleasant" way.

But this was a new day and Roessler predicted success for the shop. "They have a captive audience of about 25,000 people in the Pentagon," he said. Off Limits

The "Pentagon Tour" begins at the red doors. Tours start every 15 miniutes, they last an hour and they're free. But there's one catch. The uniformed women at the desk says once you start the tour you can't get off. And what do you see? She says, "Paintings, models of ships and planes, the hall of heroes, the flag court." You mean-you don't get to see any of the important operation? "No," she says, smiling.

A visitor sometimes may stumble onto his own tour. (This particular visitor realized he might have been off-limits when he tried to return to one place he'd already been - not exactly a top-secret command post but a cafeteria - only to be intercepted by a guard, who shouted: "Hey, where's you're I.D.? You can't go in there.") Chapter and Verse

The notice, "Lethal Area," in big red letters, was enough to catch anyone's attention. Actually, there was nothing lethal about the area. It was merely a display explaining, among other things, the "New Artillery Prowimity Fuze-M732."

A woman driving a motorized vehicle down a corridor rang a bell and everybody scattered. There was a sign affixed to the front of the vehicle that said: "Do you hate the person next to you?" but she passed too fast to get an explanation.

Near some photo displays, two small wooden blocks appeared to be screwed to the wall, possibly marking the spots where new pictures would be hung. One block was numbered 42 and the other 26. Both numbers were circled and upside down.

Down the hall, there was Escalator No. 19, Stairway No. 80, what seemed to be a typical bulletin board ("Learn to Life Right," "Tour Andrews Air Force Base, free"), and volia, an oasis in the middle of all this, the grassy, five-acre center court of the Pentagon where people ate lunch outside in glorious sunshine at circular tables covered with blue, yellow, and orange umbrellas, or lounged in deep, wooden chairs. A sign said: "Keep furniture off grass. No card playing."

An older woman sat on a bench. She was reading John, Chapter 3. She said, "It has to do with being born again. He says so right here." Which it did: "Except a man be born again, he cannot see the Kingdon of God." "God be with you," she said, as the visitor moved on.

But not before privately rejoicing in the newly gained information that the Dragon System Launcher has been simplified. Among the many money saving improvements, it's now made up of 50 parts instead of 84.