I want to take my kids some place where the entire collection of “stuff” adds up to a very unique - “Nowhere else like it."
Where is that place? Places like San Francisco, Montreal, Quebec City.

In the USA? New York City?

Since you didn't specify. Venice Italy. Or the Masai Mara in Kenya.

That's hard! Cities only? Yellowstone certainly adds up to a unique "nowhere else like it place" with an entire collection of stuff - as do many other national parks. For cities, I'd mention...
- San Francisco
- Santa Fe
- Washington, DC
- New York
- Orlando
- I would have said New Orleans before the flood. Haven't kept up with restoration progress.

ps I would like the USA and will research all of you suggestions Thanks a lot

And if we're stepping outside of the U.S., then tons more places come to mind, but I assumed you were looking for just U.S. destinations.
Abroad... Paris, Cairo, London, Beijing, Bangkok, Jerusalem, Istanbul.

Oh, and Las Vegas. And Juneau!

Grand Canyon

By the time I was in h.s. my parents had dragged me to all of the "lower 48" in a truck camper. National parks, museums, cities, you name it. My favorites were definitely San Francisco and New Orleans.

Hello sobolik, have no idea where you live but most kids love visiting San Francisco. But not sure from you comment "places like San Francisco, Montreal, Quebec City" if that means you have already been there. And of course Montreal and Quebec City are in Canada. Have fun planning your family trip.

A city is a city is a city.

Check out the USA's natural areas like our National Parks or State Parks, www.nps.gov and www.recreation.gov. This will give you more options as you travel in this beautiful country.

In the US: Lancaster, PA for a look at how people live and work today without cell phones, e-mails, text-messaging, electricity or automobiles and how a community responds to a barn fire or other catastrophe.

Out of the US: Milford Sound in New Zealand - a place to find yourself.
Mahalo! Debbie

Miami
New Orleans (still)

Whether or not kids may appreciate them or have fun, that's another question...

Nashville
Savannah, GA
Charleston, SC
Boston

San Antonio is really cool.

Charleston and Key West remind me a lot of each other except Key West is a little more 'low brow' than Charleston with prettier water.

Great Sand Dunes National Park

Yellowstone National Park, the Grand Canyon, Oregon Coast, Aspen, Highway 1 from Malibu to Half Moon Bay, Las Vegas, New York City, Chicago, Vermont, and Death Valley are a few.

Unique places in the U.S., which the kids will enjoy. Hmmmmm.

Las Vegas is unique, but it's not a kid's place.

For cities substantially different from average U.S. urban areas, I recommend New York and San Francisco.

The city of Washington DC itself is a fairly average urban area. The monuments are grander and the museums are less expensive than just about any other place in the world.

New Orleans is borderline both for its present state of tourist infrastructure and for appropriateness for children.

For natural places, I recommend Yellowstone, Yosemite, and Grand Canyon.

Anchorage, Alaska