WHAT TO SEE AND DO?
Spending two days in Köln to explore the Christmas Markets (been here before to explore the major sights, during summer). Advice on which markets to go? Other christmas-related activities?

PARKING NEAR CITY CENTER?
I am staying near the Hbf, Dom area, so I need to know inexpensive & safe overnight parking places. Where are best ones? Has anyone tried the Park & Ride areas outside of town? Are they safe for overnight parking and rental cars?

EN ROUTE from AMS?
What are best places to visit en route from Amsterdam Schiphol Airport to Koln? Been to all the major cities in NL.

There is one Christmas Market right at the Dom and another one in the Altstadt (Old Town). Both are in walking distance and even somewhat connected. So, it is easy to stroll over both.

Inexpensive parking is a problem in the City Center. The easiest would be the large parking garage DOM/Philharmonie, but not inexpensive. The Park & Ride parking lots ARE safe, so no problem.

En route from AMS, I would recommend Hoge Velouwe - a park with sculptures and an excellent van Gogh museum. And Düsseldorf, a city with many museums, and elegant shopping street, parks, riverbank etc.

And do not forget the Neanderthal Museum in Mettmann - it is an outstanding museum about the development of humans.

Thank you for the advice.

I won't have a 'green sticker', since I will be renting my car from the NL, so I won't be able to travel into the City Center.

Do all the P&R allow overnight parking? Is my rental going to be a target since it sometimes will show HERTZ on the back windshield?

It sounds like taking the train may be the better choice.

Take the train, very relaxed, and brings you out right by the Dom.

The train connection from Amsterdam to Köln is excellent. You do not need a car in Köln.

But if you have some reason to keep your car do not worry about the P&R parking lots. They allow overnight parking. Your rental will not be a target. There are no criminals.