You’re a retired senior. Your kids are grown and on their own. You are ready to give up climbing stairs, mowing lawns, fixing roofs and gutters, and worrying about the never-completed list of home maintenance items.

It’s time to sell your suburban house, with more rooms — rooms to clean — than you need at this stage of life. But where will you live?

Millions of older Americans, a large and rapidly growing segment of the nation’s population, will face that question. Most will look for an apartment, not another house, and many will prefer living in denser urban environments rather than in sprawling suburbs and exurbs.

They will decide to own and drive only one car, or maybe no car. They will seek walkable neighborhoods with convenient access to transit, shopping, cultural activities and public parks. They will try to reside not too far from their adult children and grandchildren. And as they age, they will need access to increasing levels of professional health care and living assistance ranging from occasional to continuous.

Yet, there is a big problem. Today, relatively few viable residential options for seniors exist within central cities or densely developed urban areas near city centers. Most senior housing is located instead in low-density suburbs or in small towns, where land is cheap and development costs are lower. At the same time, services for seniors in those areas are often dispersed and limited.

Large numbers of rental and condominium units are being developed within cities. But with few exceptions, newly built apartments are small — two-bedroom units are rare — and expensive. Marketed primarily to younger, gainfully employed singles or couples, such apartments are suitable for only those seniors who can live independently, who have sufficient assets and income and who are willing to leave behind most of their furniture and collectibles.

Governments, investors and developers wanting to build housing for seniors face challenges similar to those of affordable-housing advocates trying to provide homes for low- and moderate-income families. However, there is a significant difference.

Many seniors will sell their suburban homes at prices reflecting greatly appreciated value and equity. Many also will enjoy stable annual incomes from pensions, annuities and investments. Consequently, unlike people in need of workforce housing, millions of seniors will have the financial means to rent or buy spacious, conveniently located apartments.

But will such apartments — along with access to health-care assistance and resources — be available? Meeting the availability challenge will require new, aggressive public- and private-sector efforts.

Cities must adopt land use, zoning and fiscal policies that encourage and support private-sector development or redevelopment specifically tailored to meet the housing and health-care needs of seniors. Such policies must address urban location considerations to ensure that the benefits of city living — for elderly residents and the city as a whole — are realized.

At the same time, real estate developers, investors, lending institutions and health-care providers must expand their thinking about the evolving nature of the urban residential market. They must recognize that seniors who want to live in cities could represent a sizable and growing share of this increasingly diverse market. And many of those seniors will not depend on subsidized housing.

Thus, cities will need residential complexes with larger apartments — two- and three-bedroom units — in addition to efficiencies and one-bedroom units. And motivated housing developers must collaborate and partner with health-care entities to provide medical service options when and where needed.

Eventually, cities such as Washington could be populated by a richer mix of young, middle-age and older inhabitants. That would be a plus for retail, restaurant, recreational and cultural destinations; for nonprofit institutions needing volunteers, and, of course, for health-care providers.

Other benefits would accrue. Seniors are a fiscal plus for cities, generating additional tax revenue but not additional public school students. Traffic congestion and parking demand could decrease as older and younger citizens opt to drive less, choosing instead to more frequently walk, bike and use transit.

Of course, there always will be market demand for housing for the elderly and health-care facilities in U.S. suburbs. But a potentially large market for seniors who want to reside in cities has yet to be tapped.

Roger K. Lewis is a practicing architect and professor emeritus of architecture at the University of Maryland. His cartoon drawn for the column may be seen at www.washingtonpost.com/realestate .