Don't be fooled by its fortress-like exterior; stepping into St. John's Co-Cathedral is like entering a different world. Every surface of this Baroque masterpiece is covered in gold, intricate carvings, and stunning frescoes, creating a breathtaking contrast you have to see to believe. As you walk across the incredible marble floor, a mosaic of knights' tombstones, you'll feel the immense history of the place, culminating in the dramatic sight of Caravaggio's famous painting, 'The Beheading of Saint John the Baptist.' It's an essential Valletta experience, with an adult admission fee of €15.