The Hyrule Castle Town Ruins are located directly north of Sacred Ground Ruins. Little of the town still remains. Most of it being destroyed and burned to the ground during the Great Calamity. The ruins are littered with Guardian Stalkers and Decayed Guardians. Link can find many Treasure Chests hidden in the walls under spires.
Many of the houses and castle walls protecting the town are destroyed and covered in Malice. The ground is blackened and covered in ash and poisonous Malice. So much of the buildings are destroyed, nothing is obstructing Link's view of the entire town, putting in perspective the true demise of Hyrule Castle Town.