My mother-in-law lived her last years in a retirement community where she was fortunate enough to find love with a wonderful man and remarry. Save for the staff, though, she spent her days exclusively with the old, after a lifetime of friendships with people decades younger.

Children were hardly encouraged to visit. They were banned from the dining hall, even on holidays, and there was no place to play, not even a swing. Kids came to be viewed as apparitions running down walkways. The place resembled a sanatorium, but not in a colorful, Thomas Mann sort of way.

We came to think of the “village” as a ghetto, a genteel, white-haired ghetto, but a forced community of sameness surrounded by more retirement developments shielded behind manicured shrubs and gates, all order and removed from quotidian life.

It may take a village to care for a senior, but not one occupied by children or unpaid younger adults.

There’s clearly a need for professional care for the elderly, especially those in declining health on limited incomes, but my husband and I hope to enjoy our later years among people of all ages.

Preferably in Italy, though Spain might do.

All ghettos are failures, whether based on poverty, age or, as is increasingly the case in provincial towns such as Manhattan and San Francisco, wealth.

Those bicolor maps remind us that we pick our neighbors for their politics, too, which is comforting but deceptive. It lulls people into a downy complacency of believing everyone is like them, while masking the insistent truth.

A full, rich existence, one that sparks the mind as well as the senses, derives from the interplay with people unlike us. This is why I felt it necessary to leave Washington after all the cocktail-party chatter that began, “And where did you do your undergraduate work?”

Without the extraordinary, the unexpected differences, a challenge to our accepted norms, life loses definition. It bleeds out over the edges until there’s no contrast, and little color. Daily life becomes as bland as retirement-community food.

One of my favorite people is north of 90, a spry, engaged woman who goes out more than I do, taking courses, attending theater, devouring books and lectures, engaged in daily flights of the imagination.

We’re recent friends and, had she lived in one of those retirement homes, might have never met. At twice my age, she has the life I always thought I’d have by now, and she gives me hope. She’s too smart and funny to traffic much in nostalgia — that’s the province of people who have stopped enjoying new experiences, a dull plateau that can be reached at any age. No, she’s busy ingesting the now, while wearing her knowledge and experience as beautifully as her refined clothes.

Another favorite person is an ebullient 17-year-old, who’s not solely consumed with her navel. (It’s fitting that so many girls have taken to exposing and piercing the body part that best exemplifies their self-absorption, the sartorial equivalent of a poker tell.) My friend is completely engaged in the world, politically and socially active, a champion of the underdog, who can’t wait to make a difference. She’s never put off by age, becoming pals not only with her mother’s companions, but with those of her grandmother as well. She’s a social omnivore, curious and engaged.

Being with both women — one twice my age the other, well, never mind — draws sparks as time spent with peers often does not. Left to our own devices, stuck in an orbit of clones, we can quickly break into a litany of complaints about everyday garbage, the bland familiar. It may be comforting, even a brief tonic, but does nothing to place us in the larger world.

Ghettos can exist in the mind as easily as behind manicured shrubs. As noted, you can reach that dull plateau in no time flat. It doesn’t require old age to drive you there.