Itinerary Suggestions

Spain!! All of the above, and more!! Madrid for a couple of days.....Segovia and Toledo....hiking in the mountains north of Madrid....the Andalucian circuit down through Cordoba and Sevilla and over to Granada....the "white villages" in the southern coastal mountains, prehistoric wall paintings, massive Roman ruins, tapas, Rioja wine, very late nights, a "joie de vivre" unequalled anywhere else....and probably the cheapest prices in western Europe.

Well...Spring can mean a wide range of possibilities, and while your focus will wind up South, the focus would be on Food and Culture as opposed to beach, which would need to wait until late May, So I would consider one of the following:

A Spain/Portugal swing

Maybe do more of Italy (Florence, Rome, Tuscany. Naples, Sicily?)

Paris and France to the South.

Turkey

In regards to other areas, Greece is a bit of a shame to do without the Islands and warm weather, and even Spain without the coast or the islands lacks a bit.

Spain is a good idea--also put Turkey on your list of destinations to consider!

France has much to offer for your interests since you haven't been there. I especially liked the Dordogne for hiking/caves/small scenic towns, and Carcassonne/Avignon/Arles for history. But I also enjoyed Normandy and the Loire Valley. The RS book on France has great ideas, look at his 2 and 3 week itineraries for a good trip.

"Interests: Ambiance more than seeing every sight, medieval buildings, villages, churches, castles, big markets, hiking, less crowds the better."

You've been to Amsterdam, but apparently skipped the rest of the Netherlands, and you haven't been to Belgium, Luxembourg, northern France (Lorraine? Champagne?), or the Mosel River. These places are not far from one another and provide precisely the sort of experience you are looking for.

Some specific places I've liked that you might look into:

Netherlands: Keukenhof gardens (spring means tuliips!) and the surrounding Dutch countryside; Zaanse Schans village; Monnickendam, Volendam; Delft.

Mosel villages, especially Bernkastel and Cochem (good hiking areas near these too): www.mosel-reisefuehrer.de/moselhighengl/moselhighlightsengl.html

Belgium: Bruges (popular, but fantastic), Antwerp, Ghent; Ardennes villages (Dinant, Durbuy, Spa, and WW II villages of La Roche en Ardennes, Stavelot, Malmedy

Belgian castles and fortifications: http://www.visitbelgium.com/index.php/castles-and-gardens

Near the Belgium border in Germany: old weaver's village of Monschau: http://www.monschau.de/touristik/bildergalerie.php?bereich=Altstadt (click through photos.)

Luxembourg castles, historical sites: http://www.visitluxembourg.com/Sites-Attractions.htm#HistoryLandmarks

Thanks to all for your suggestions - actually helpful with the examples of what to see especially. We actually managed to get a train down the Mosel to see Burg Eltz while we were staying in Bacharach our first trip. I probably should note we'll take trains and not rent a car and spring has turned into early summer - so late May/at the most first week of June. Also, more into medieval/older history. So, no intention of doing a Normandy visit I think on this trip.

Thinking either Spain(with a Morocco visit) or France/Belgium (perhaps Lux)or Slovenia/Croatia/Bosnia (or maybe leave off Slovenia and do a couple days in Montenegro). I've noticed in the Croatia/Slovenia area taking trains is more challenging but doable and similarly Spain is a very big country! Also, from Boston flying into and around Croatia is VERY expensive and long. Had initially thought we would do some southern Italy and fly into or out of Rome (and utilize the overnight ferry from Bari to Dubrovnik) but he is leaning away from Italy for this trip in particular.