Places to pause. They welcome the visitor from the sidewalks of the city: Boston's lobbies - venerable, spacious, famous - are an attraction in themselves

A LOBBY is an expression of wealth and power; it's the architectural equivalent of dripping with diamonds. Any building grand enough to have one has an idea behind it, beyond the mere rootling for survival. The lobby expresses that idea, gently indicating the aesthetic appreciation, reverence, or nostalgia you should feel as you head for the prosaic, even grubby, floors where actual work takes place. Says Boston architect Todd Lee, ``If [a lobby] doesn't explain what goes on in the building, it hasn't done its job.'' Lobbies are, as they say, where you find them; and a true aficionado learns to look through half-open doors and read fa,cades. The pastime can be practiced anywhere. But cities like Boston - old, gracious, full of antique structures - offer especially rich pickings. A ramble through Boston buildings tells in its particulars a larger tale of lobby-as-art-form.

Not all lobbies are grand, of course. Lobbies of churches are a good example. Everyone feels awe at a church's soaring spaces; but who notices the lobby, a small, often low, and plainish area? And yet going from the lobby into the church is what gives you the subtle feeling of moving from the ordinary to the extraordinary, out of darkness into light.

One of the strangest lobbies in Boston is in City Hall; but then, City Hall is a very strange building. It has an odd weightlessness, as if lightly tethered to the ground by means of its pillars; it squats over the lobby like a monumental concrete chicken crate brooding over a rectangular glass egg.

The brick plaza outside flows straight into the brick floor inside. People walk through, striding along with swinging arms, as if they were outdoors. You can see a number of Boston landmarks through the windows; you feel a part of the whole city here.

This is a friendly home for civic causes. Two short-haired women in slacks and cardigan sweater vests are creating an enclosure for a meeting by briskly tying blue balloons to the stair railings; the balloons say ``Office Workers' Pride.'' A bearded man at a nearby table signs up people for a Walk for Hunger. ``Bring your friends,'' he says kindly.

There is not a great attention to aesthetics; Japanese stone lanterns, pianos, things like that, get shoved into corners, unless they are wanted for some event. You feel like taping your own sign on the wall; there is a feeling that here your needs are legitimate.

Very different is the lobby of the State House, home of the Massachusetts legislature, which is full of appreciated and beautiful things; all Roman grandeur and martial themes. Nineteen kinds of marble are used in the arches and stairways; it's almost worth coming here for the mosaic floors alone. This lobby is a history lesson: There are frescoes of Paul Revere's Ride and the Boston Tea Party, for instance, and famous governors and heroes in bronze.

``The notion of lobbies as public rooms that furnish meeting places for different kinds of people is the height of what makes civilization in a city,'' says Mr. Lee. ``If we don't provide public spaces - and many of them need to be interior in a climate like ours - I think you end up segregating elements of our population, one from another; and you lose a lot.''

If this were a hotel, you wouldn't dare walk in the door in street clothes; as it is, schoolchildren sit on the floor or run shrieking down the marble stairs.

Some volunteer guides called the Doric Dames will show you around and explain what everything is. My favorite item is a beautiful stained glass window that shows the evolution of the Massachusetts state seal; the original, designed in England, features an Indian who is saying, ``Come over and save us.''

Hotel lobbies, on the other hand, put a burden on the visitor; they reproach jeans and untidiness. A really first-rate hotel appeals to fantasy: We are rich and important and lead golden lives.

The prime function of a hotel lobby is to separate the exhausted traveler from the world outside. Hotel lobbies allow you to adjust your thoughts from the hurly-burly; that is why they so often have velvety carpets and restful flowing lines.

One of the most visitable hotel lobbies is in the Copley Plaza.

The Copley Plaza is a hotel for Anglophiles. A doorman opens the door for you and you drift elegantly up a long, narrow hall lined with Chinese cachepots on tall tables, discreet cases of items for sale on the walls, under a ceiling that is a series of little blue domes. When you reach the lobby, all you see are brilliant, luxurious surfaces: crystal chandeliers, ornate gilded ceilings, electric blue custom-made carpet, marble pillars. You can sit in the Tea Court and eat scones and dream of Empire, surrounded by palms and a marble balustrade.

``One of the things about the Copley Plaza lobby: Because it has more height than the Ritz, it's able to work better as the focusing of the energy of that hotel,'' says Lee.

``It can accept, usually with grace, the crowds that come out of the ballroom,'' he adds. ``It's better when they're in white tie, of course. That's a wonderful lobby to go to a waltz evening in. And that animates the lobby, in turn.''

A lobby should be an entranceway, and the lobby of the old Boston Public Library isn't really that anymore; to get there most people enter the new building on Boylston Street and take a left through little corridors and past a secret courtyard.

Entering the old way, you are greeted by the statue of Henry Vane - in cocked hat, lovelocks, plume, and boots - and, on the heavy doors, various bronze ladies in drapery.

It's a backwater now; a guard sits indifferently at a desk, a few people wander absently through. But still the ceiling has its domes and mosaics - twining vines and the names of great 19th-century authors. A broad stairway with windows at the top draws you; you float upward, drawn to the light, between two long-nosed lions, library lions, proud but not unfriendly.

``The Boston Public Library is probably the best expression of a Boston lobby, partly because everybody with their pennies paid for it; that makes it doubly precious,'' says Lee.

This lobby was plainly designed when scholarship meant the study of classical thought, as reflected in classical architecture. The marble is the immensely learned-looking color of old books. There is everything you could want in the way of a pillar and a pilaster, as well as classical frescoes of robed figures frolicking by a classical blue sea.

In one golden alcove sits a gray-haired woman, austere and thin. She looks ragged but intellectual: silver tape on her feet, with holes in the toes. Is she a bag lady? A college professor? Her hair in a bun, she could be a classical figure, too - representing, perhaps, The Human Spirit. A lofty pile of books next to her; she rests the top one on the pile and bends over it and mutters, reading aloud.

Small sounds here make huge echoes, the aural equivalent of a tiny figure in a searchlight casting a giant shadow. There is a continual vast hum, like a thousand people thinking.

People are the only things in the lobby that change. They shuffle through quickly, on loud echoing sneakered feet, and are gone.