"Some of us are on the brink of catastrophe," Milwaukee's Mayor Henry Maier told a three-day meeting of the U.S. Conference of Mayors that ended here last Monday. "If you don't believe me, go look at those bond ratings . . . We have city after city onthe verge of collapse."

Maier's gloom, echoed by virtually every Front Belt mayor, seemed justified on the surface. Not yet registered by statistics, however, are new, hopeful signs that America's suburbanization (and corresponding decline of the "urbs," the old cities) is coming to an end.

One of those signs is the still accelerating extent of "recycling" of old buildings and new "infill" construction rising on vacant lots or underused plots of land within the city boundaries. Only a small part of this is visible as yet. The larger part is still on the architects' drawing boards -- the most reliable indicators of the urban economy a year or so hence.

As yet, there is little improvement in the inner city ghettos since the 1969 Kerner Commission report told white America about the black condition. The new administration seems intent on cutting federally supported housing and social programs.

The census says the cities are still losing population to the sun belt in search of jobs and to the outer fringes in search of affordable housing.

But, in contrast to what happened in the heydays of suburbanization, now the less then affluent are leaving the old center cities. The affluent seem to be coming back. Most eastern cities, notably Washington, are making room for them and their business.

There is plenty of room. One of the myths that plague rational urban policy discussions in this country is that our cities are overcrowded. They are undercrowded, suffering deadly anemia and heart disease from too many parking lots, vacant lot, empty buildings, idle railroad yards and business districts that do business for only eight hours in 24.

An example of this anemia was the East Capitol Car Barn in Washington, a magnificent Victorian "castle," that stood empty since Washington's streetcars died in 1962. It is being recycled into condominium and rental apartments. The architects are Martin & Jones, one of many young firms that specialize in relatively small projects that, one by one, promise to restore not only nice antiques, but also the city's health.

This one two-man firm is doing six other jobs -- some with previously unheard-of features. The unheard-of feature of Martin & Jones' building at the corner of M and 29th streets in Georgetown is that it contains offices, apartments and a branch bank under one Neo-Georgetown Post-Modern roof.

Unheard-of about the high-rise condominium at 2301 Washington Circle is that it owes its design to its neighbors. They insisted that it include three old townhouses and that the design be entrusted to architects who are more sensitive to the style of the surrounding buildings than the developers' first architect.

Martin & Jones belong to the still immature but perhaps talented school of young architects who demonstrate their contempt for the bare and square modern style of yesteryear by dressing their buildings with capricious and oversized Las Vegas ornaments and equally capricious and oversized round arches. One of M&J's townhouses has a Las Vegas-style Doric column stuck on to it, for instance. Another shows round brick arches, arching nothing in particular, growing out of a glass roof.

Such fads pass. The important aspect of these designs is that for the first time since architects became technocrats early in this century, they are trying to adjust their buildings to the existing old city, rather than expecting the dear old city to adjust to their megalomania. Architects are again beginning to respect urban values.

One such successful attempt, the expansion of a Tudor-style apartment house converted into an office building at 19th and I streets NW, just received a distinguished design award from Progressive Architecture magazine. rThe architects, Tom Kerns and Bob Anderson and their team, added four stories, each representing a stepped-back replica of the original Tudor roof line. It is remniscent of architect Hardy Holzman Pfeiffer's idea for the addition to the old Willard Hotel.

"We have seen a number of unsuccessful and labored attempts to design old buildings that fit into the contextual neighborhood," said Washington architect George Hartman, one of the jurors. "This one, at least, is not silly or unrelated to what's around it."

Another example of effective infill is the proposal to build new houses over the old Glen Echo streetcar tracks along the C & O Canal.

Recycled and infill buildings in the city have tremendous advantages over new buildings out on farmland. All the necessary public services, such as roads and utilities, already exist. Their users do not have to commute for work and recreation. They also save energy because city buildings huddle together for warmth. Nobody needs to be displaced by them.

Most of all, they save the nation the prohibitive cost of further urban sprawl.

No two cities are alike in their potential for infill, says real estate researcher Deborah Brett. "In many metropolitan areas, the amount of infill land is extensive -- more than enough to accommodate development activity for the next 10 years."

Many infill parcels are small and ownership is fragmented, says Brett. In many instances the owners, speculating that land prices will continue to go up, refuse to sell. Cities may have to revert to urban renewal powers to assemble attractive development sites.

Many developers, Brett found in a nationwide study, are still reluctant to move into the center city and not only because prices are higher. City people are expected to mind their manners -- architecturally and otherwise. They are expected to conform and to listen to their new neighbors. Developers are generally accustomed to being able to do as they like out in the potato fields. g

Infill and recycling opportunities downtown are not likely to meet the demand for new and affordable housing. But it does help to bring money back into the city.

Together with the downtown construction boom -- in Washington, Baltimore, Boston, New York and other East Coast cities -- it should be some consolation for ur desperate and angry mayors.