Let the tourists take over the Smithsonian and National Gallery this summer.

Save some out-of-the-way treasuresfor yourself. There are unheralded museums, some reflecting the taste of a single collector, others a melange of art and furniture. Some have pieces that rival the larger museums.

One of these is Dumbarton Oaks in Georgetown. Though the collections are closed July and August, the gardens remain open. The building and grounds are a true labor of love, reflecting the cultured and educated taste of the last owners, Mr. and Mrs. Robert Woods Bliss. Mildred Bliss, along with landscape architect Beatrix Farrand, meticulously created the finest American example of an 18th-century European garden. Sixteen acres of terraces, flowers, trees, exquisite mosaic pebble fountains and vast expanses of well-manicured lawns. It is elegant and classy right down to the ribboned cement trim on the brick walks.

It's too late for the explosion of spring flowers and too early for the autumnal show, but there are many flowers in bloom now, including 37 varieties of roses.

The Federal-style mansion houses the Bliss collection of Byzantine and pre-Columbian art, the latter dramatically showcased in an adjoining glass pavilion designed by Phillip Johnson. While everyone else was preoccupied with collecting post-Impressionist art in the 1920s, the Blisses were acquiring ancient works - when any but archaeological interest in these periods was considered "odd."

The Blisses' spare taste in art contrasts with the lavish pieces of another collection. West of Rock Creek Park resides the most eminent assemblage of Russian Imperial treasured outside the Hermitage in Leningrad. Hillwood, the estate of the late Marjorie Merriweather Post, is larger than Dumbarton Oaks but lacks its sophisticated elegance. The driveway is lined with fragrant shrubs and evergreens. The grounds are an impressive sweep of thick grass and tall trees.

Inside are more prime specimens of 18th-century French royal porcelain, tapestries and antiques than you ever imagined existed, let alone dreamed of living with. The Russian Imperial collection includes some of the exquisite bejewelled and enameled Faberge eggs, (which the czar's family members gave as gifts at Easter, the most important holiday for a Russian Orthodox Christian), as well as ornate icons and choice porcelain.

While it's nice that the tours are limited to 25, reservations must be made far in advance. Considering the enormity of the collections, docents rush visitors along. And the mansion is wired. One step off the plastic protective mats triggers an alarm and you may find yourself suddenly surrounded by security guards.

The introductory multi-media stereo-phonic slide presentation, narrated by Mrs. Post's daughter, actress Dina Merrill, is too programmed (its dramatic approach may remind some of the secret cloning orientation session Woody Allen witnessed in his futuristic movie "Sleeper"). My impression is that the nouveau riche Mrs. Post, a native of the Midwest, calculated to make herself go down in history as the first queen of America.

Another example of the urban lifestyle of the very rich is Anderson House, now national headquaters for the Society of the Cincinnati - whose membership is limited to the first-born male descendants of Revolutionary War officers. Richard Clough Anderson was one of the founders.

Between diplomatic assignments, his great-great-grandson, Larz Anderson, built this beaux arts structure in 1904 with grand-scale entertaining in mind. The large reception halls with elaborate marble inlay floors and majestic stairways were modeled after European originals that struck his and his wife's fancy. One has grand pseudofrescos detailing Andersons in the Revolutionary and Civil wars. An 18-century French-style drawing room mixes antiques from Versailles with reproductions, a common practice at the turn of the century. When they couldn't import the original, the Andersons commisioned artisans to come here and recreate - as they did with the beautiful handcarved panels in the dark dining room.

Through his Foreign Service posts and travels through Europe and the Orient (when it was permissible to accept gifts from foreign governments), the Andersons acquired an electric collection of art - including a Han dynasty vase, 19th-century Japanese screens, medieval and Renaissance religious works from Europe. Unlike Hillwood, you are free to examine the pieces up close at your own pace.

It becomes apparent that the rich have the ability to materialize their fantasies. Anderson even commissioned gilded sculptures depicting characters from the children's books his wife wrote.

For museum visitors with a taste for Art Nouveau there is the Scottish Rite building - headquarters for the Supreme Council of the 33rd and Last Degree of Ancient and Accepted Scottish Rite of Freemasonry - completed in 1939. The designers of this structure placed much importance on symbolism and drew heavily on Egyptian and Greek architecture. Outside, guarding the entrance of the Greek-style temple, reside two colossal sphinxes, representing Wisdom and Power. The upper level, which houses the temple room, is surrounded by 33 Ionic columns, each 33 feet high, symbolic of the mysticism of the number of 33.

Each degree is earned through charitable deeds and other acts that the Freemasons are not exactly open about. The docents give adequate details about the physical layout of the building, but any questions about the Freemasons go unanswered.

The formation of the secret society is sketchy.Robert Burns was one of the principal founders in 18th-century Scotland. George Washington and other Revolutionary War heroes were also members. Many past and present members distinguished themselves as prominent military and political leaders in this country, notably former President Gerald Ford and Harry Truman. Hitler banned them.

Inside: A visual feast. Exquisite alabaster lamps with elegant bronze candelabra line the grand entrance hall. Chandeliers modeled on a Greek basin vase, executed in bronze with an inner alabaster bowl, are present everywhere. Marble is plentiful - floors, walls and tables. The temple room is the best treat - dramatic, with an ornate dome, lots of deep green granite, brass trim, black marble and hand-rubbed Russian walnut furniture.

Down 16th Street at Scott Circle is the National Rifle Association's firearms museum. There are about 1,400 firearms on display, representative pieces used for game and target shooting. The only military arms in the collection are those converted for recreational use.

Some are beautiful. The Japanese ceremonial temple guns have exquisite mother-of-pearl inlay and intricate filigree. The Japanese developed a matchlock system for ignition using a burning wick. They also shot from the cheek rather than the hip or shoulder. There are equally ornate antique shooters from Pakistan, India, Algeria and Persia.

There are, of course, some legendary pieces. Theodore Roosevelt's favorite gun, a Winchester model 1876, 45-75 caliber - a heavy rifle by any standards. The history of handguns in Europe is depicted, including the famous German Mauser pistols, Henry Derringer's pocket pistols, an early English fowling pieces owned by King James II, dueling pistols and a rifle belonging to Napoleon Bonaparte.

Around the corner from the National Rifle Association you can find another glimpse of the past. The area's largest collection of Jewish ceremonial art resides at B'nai B'rith Klutznik Museum. The acquisitions are primarily from 18th-and 19th-century Europe, the periods reflected in the designs. There are illuminated manuscripts, Scrolls of Esther, a stunning breastplate for the Torah, a selection of elaborate Hebrew clocks.

Bearing in mind the frequent dangers of possessing Jewish paraphernalia, the craftsmen evolved clever disguises for religious materials used in oppressed areas. An intricate miniature Hebrew Bible, one inch high and 3/4 inch thick, could pass for a phill box. The writing is so tiny that the book came equipped with a powerful magnifying glass. Other traveling religious articles, beautifully engraved, were shaped like catechism books.

Another museum piece is the Woodrow Wilson House. While this stately home is elegant and charming, it is the professional working kitchen that I like best. The utensils used at the turn of the century are very similar to those around today. If you think the crock pot, vegetable slicer or meat slicer is a recent creation of technology, you are a victim of revisionist history. They operated without electricity. The typical hearty breakfast then was cooked overnight by placing the pot with oatmeal and water on top of a well-heated stone in an insulated, covered tin box. Fruits and vegetable were washed in a special deep-basin sink. The drainboard is slanted and the drain partially covered to prevent clogging.