City of Solitude

• WWizards of the Coast2004-10-04
  Official Ruling
  City of Solitude can affect abilities of cards that are not on the battlefield because it prevents players from activating those abilities.
• WWizards of the Coast2004-10-04
  Official Ruling
  City of Solitude does not stop triggered abilities from being put on the stack. They are never “activated”.
• WWizards of the Coast2009-10-01
  Official Ruling
  This stops players from activating mana abilities.

Rulings via Scryfall