Gamla Stan (Old Town) is Stockholms historic medieval heart and one of the best-preserved old towns in Europe. Dating back to the 13th century, this atmospheric quarter spreads across three islands with narrow cobblestone streets, colorful merchant houses, royal palaces, and ancient churches. Key sites include Stortorget (the main square), the Royal Palace, Stockholm Cathedral (Storkyrkan), the Nobel Museum, and Marten Trotzigs Grand - Stockholms narrowest alley at just 90cm wide. The area witnessed the infamous Stockholm Bloodbath of 1520.