Can’t quite reconcile “outdoor trip” with London, Brussels, Amsterdam and Paris. These cities probably have more museums per square block than any other cities on the planet. Unless your idea of outdoors is a sidewalk cafe on a busy street or a city park (many of them huge and very nice but utilized by millions — that’s plural — of residents), you seem to have picked the wrong places.

2 days stays means 1/2 day to get there, 1/2 day to get to your hostel and get oriented to your new neighborhood leaving 1 day for either hectic city sightseeing (that’s museums and other sight-seeing attractions) or a hectic day trip to get outdoors to a somewhat less urban locale. Follow this up by getting up early the next morning to do it all again in a new city.

What are your plans for 6 days in Paris?