I have a six hour layover in Amsterdam. Flying PDX to WAW. The 1 hour layover didn't seem long enough so other option in 6 hours. Suggestions of what can be done close to airport!? Thx

If you can still book it with the 1 hour layover, on one ticket, I'd still do that. If you miss your connection, you'll get put on the next flight to WAW six hours later anyway at no cost to you. Amsterdam Schiphol airport is a pretty efficient airport. (If you booked your ticket less than 24 hours ago, you can still cancel it for a refund and re-book.)

Six hours is barely enough time to get the center of Amsterdam and back and have an hour there, after you factor in immigration and baggage claim just arriving and the need to get back a few hours before departure, to go back through security and passport control. But, you could arrive early. I'd play it by ear upon arrival - but, going into the center of Amsterdam is probably what I'd try to do: take a train to Amsterdam Centraal and just walk around for as long as I had, then go back to the airport.

You can't get into Amsterdam and back (or anywhere else for that matter) with a six hour layover. Schiphol is extremely busy and queues for security can be very long. Even for a European flight you need to be there at least two hours before your departure. By the time you have cleared passport control, got your train ticket and got into Amsterdam it will be nearly time to turn round and head back again.

Either try to change to the one hour changeover or just spend the time reading, people watching, using the free WiFi.

You may be able to do a Behind the Scenes Schiphol tour I guess, but that will involve going landside.

you won't have time

check out the Rijksmuseum's Schiphol branch!

https://www.amsterdam.info/airport-museum/

I guess there is some kind of mini red-light district too?

Good news is there are worse airports than Schiphol to spend 6 hours. That's really not enough time to go anywhere else.

From Schipol to Amsterdam centrum is a pretty far distance, it will take you around 2hours way and back, so you'll be left with no time to visit anything and you won't have the mood to enjoy it knowing that you may miss your flight. best things is to take the 1h layover and come back when you have time. Amsterdam is not a city you wanna say I spent 4 hours in

Passport control at Schiphol took us quite a long time, 45 minutes, a few weeks ago.