Riddarholmen is an island in Lake Mälaren and a neighbourhood in central Stockholm. 
Riddarholmen together with the Old Town are The historic centre of Stockholm. In the 13th century a monastery was built and the abbey church, the current Riddarholm Church. During the 17th century, the nobility built magnificent palaces that later gradually taken over by the state agencies and courts that still dominate the islet. 

Walking distance to Old Town shopping streets, restaurants, etc.