These cool, pine-forested peaks high above the resort-encrusted Catalonian coastline are often called the "Crown of Aragon," stronghold of James I. The Prades Mountains, Mantunyas de Prades in the Catalan language, remain a quiet retreat from the cares of the world.
The mountains are developed primarily for eco-tourism, with natural parks, fantastic camping opportunities, hiking trails, rock climbing, and many other attractions for active tourists. Ancient towns hewn from stone atop impossibly scenic outcroppings offer a dose of culture, such as the castles of Siurana (Priorat) and Prades, and Monastery of Santa Maria de Poblet.
A high-speed train between Barcelona and Alicante stops in Tarragona, the closest major tourist destination to the Prades. The coastal resort town has hotels, tour operators, and car rental service, and buses into the mountains.
The Prades Mountains, however, do not lend themselves to independent exploration via public buses, though adventurous types with some Spanish (or Catalan) skills and plenty of time can certainly do it. It's much easier to either rent a car or book a tour.