Probably the most unique feature of Stockholm is the wonderful archipelago that is home to the city and spreads out from it, a long way into the Baltic Sea. 20 to 30 thousand islands wait to be explored in this amazing area. There are plenty of ferries (some are historic steamers, others modern and surprisingly quick) that go from the quays in the centre of the city.

The Vasa Museum, displaying the worlds only  surviving 17th-century ship, is truly amazing. The ship is almost completely intact and entering the main hall is quite breathtaking, even on return visits. Don't miss it!