Where would you go in late March?

Spring skiing in Austria! Söelden was great and there are many ski areas!

Or France 🤔 or The Dolomites.

Don't ski?? Then I would suggest Salzburg and Venice. I visited these in March 2017 and had great weather.

Enjoy the planning and the trip!

The orange and lemon trees will be blossoming in Spain and Italy. Their intoxicatng perfume wafted throughout Valencia and Andalucia when I was there last year in March. The last week of March is Semana Santa - a very special time throughout Andalucia but especially in Sevilla and Malaga. I was in both and much preferred the processions and atmosphere in Malaga, but I love Sevilla and Cordoba (whose celebrations are more somber) as great tourist destinations. I was in Sicily at the end of April a few years ago and the wildflowers were incredibly colorful and plentiful. I would guess that they start bllooming by late March. Then there's Naples and the Amalfi Coast. Just choose wisely for Easter weekend.

We often travel that time of the year, and most years the Winter weather has broken by that time in Austria.
I would suggest Bratislava as a side trip from Vienna--39 miles and a bus ride away. But it's a whole different world.
Salzburg is another very popular city easily reached from Vienna by train.
Cesky Krumlov is another popular city North of Linz, Austria in the Czech Republic.
Flying home, try flying through a city like Lisbon, Portugal for that time of the year.

I think that once you get into April then you can make anywhere work. Go with your heart.
I do like the suggestion of Lisbon however.

For better weather, head to southern Europe, as March can still be rainy further north. Nowhere is going to be hot at that time of year.

Schools are on Easter holidays the last week of March and the first two weeks of April, so you will notice a spike in air fares and hotel prices that corresponds.

Spring flowers will be out in southern Europe including Portugal, Spain, Italy and France. Lisbon and Porto are a more manageable size than say Paris.

I am spending mid February/early March in Fuerteventura, one of the Canary Islands with great volcanic scenery, then I am heading to Portugal for a month from the third week in March. This year, some days in London were warmer than Spain and Portugal in March, but that's unusual.

Greece and Turkey offer the same springtime benefits mentioned elsewhere around the Mediterranean. And Greece could allow you to experience a second Easter - 4/1 for the western rite churches and 4/8, 2018 for the orthodox churches - as Rick did when filming his Easter special.

In late March/early April I would go to Paris. I know my answer does not fit into your desire for a smaller place. True, it is easier to come up with places to go to in May than March.

You will find that flights to many places in Greece do not start operating until early May. There is a reason for this ie the weather! Some Greek resorts will be still closed for the winter in March.

Thank you for the great information. Very helpful to know about school vacations and holidays to consider. Lots of ideas to research and think about - and I love that part of the process 😊

Portugal! Porto, Guimaraes and Lisbon are my favorite cities.

I am falling in love with the idea of Portugal. But Slovenia has been a dream for awhile now and it's right next door and wouldn't require another flight. The weather in Portugal would be better, but better weather brings more crowds. Decisions, decisions!

Northern Eastern parts of India are great places to visit in Feb, March and April

Not quite convenient to Vienna is it?

Hello amosk. You said you desire to go to Slovenia. Yes, Slovenia is a good vacation destination. Slovenia has several elements that American people like to see in Europe. And, Slovenia is located at the "sunny side of the Alps". I recommend :
Train from Vienna to Salzburg. Be at Salzburg three nights. Bicycles can be rented there, for a ride along the river. Can bicycles be rented in April ? I do not know.
Train from Salzburg to Ljubljana. I think that is a five hour train ride.
Fly from Ljubljana to the United States of America. The flight departures from the Ljubljana airport are at early times in the morning. You would transfer to an other airplane at an other airport in Europe. You might want to look at United Airlines.

Fly to Milan, visit the Duomo then go see The Last Supper ... next day take the train to Tirano where you catch the Bernina Express through the Alps (stopping in St Moritz for a few hours if time permits) to Chur where you connect to Zurich ... spend a day there (must see Chagall's 5 stained glass windows in the Fraumünster church) before flying home. Did this last Christmas time (except we went from Zurich to Milan with a stop at Bellagio on Lake Como for a half day and night since we had already seen the Milan sights on a previous trip) in 4 days.

Or how about Barcelona?

Not a fan of Lisbon. Dirty, sights mediocre except for wonderful Aquarium. None of our charge cards worked at Metro stations.