I think of Iceland as Europe. It is about 3h plane ride from Amsterdam and 3 and a half from Paris. In my book, that makes it the perfect place for a long week-end. 4 days will not get you far as the island is huge but it is possible to cover area around Reykjavik, visit a scenic waterfall and the famous geyser.
You have a choice of holidays on the Icelandair website. I decided for a Northern lights tour and a visit to one of their geothermal baths: http://www.icelandair.co.uk/offers-and-bookings/book-packages/package/item747151/northern_lights_and_hot_springs_/.
We were based at Icelandair Natura hotel. A no frills place, a bit outside the city. I would however recommend looking for something in the capital to truly enjoy all the food and bar scene.
One of the places you should visit for dinner is the Fish market (http://fiskmarkadurinn.is/). They prepared fish like nothing I have tasted before. Raw or cooked, they did a great job mixing flavors and flawless presentation. If you want to spoil yourself, get the tasting menu and a seat in front of the kitchen. You will talk about it for weeks after leaving Iceland.
The hotel helped us organize additional trips and activities. The Iceland Golden circle is a good choice to take in the main sights: the Geysir geothermal area where the Strokkur geyser shoots a column of water up to 30 metres, Gullfoss (Golden Falls) waterfall and finally the Thingvellir National Park, where the American and Eurasian tectonic plates are pulling apart at a rate of a few centimetres per year. The Park is also the setting of the scenes at the Wall in the the Game of Thrones saga. On a wintery day (that may happen from October to April in Iceland), you can definitely imagine John Snow making an appearance.
The final highlight of the trip was a late night break at Laugarvatn Fontana´s open air geothermal baths. In March it was still below 0 in the night. Which is fine when you are covered in steaming water (around 36-38 degrees C) but makes you run quickly back to the dressing room when leaving the pool. In hindsight, I should have foreseen a bathrobe.
He main show, the Northern Lights, were more difficult to point down. We have tried two ‘hunting’ trips but the sky was covered and the aurora borealis did not make an appearance. Another activity I would have liked to do is diving the rift between the tectonic plates but time was too short and wether definitely too cold. I kept the positive attitude- that is a good reason to go back to Iceland. That, the great food at Fish Market and a whole lot of natural landscapes that wait to be uncovered. Do not forget your camera!