The river-basin of Central Catalonia is that of the Llobregat, near whose estuary Barcelona stands. Its lower course lies through the level ground along the coast, but its upper waters and those of its tributaries drain a series of highland valleys, difficult of access and divided from each other by considerable chains of hills. All these valleys unite at the foot of the crag of Montserrat, which, crowned by its monastery, overlooks the plain, and stands sentinel over the approach to the upland. In the mountains behind Montserrat was the main stronghold of the Catalan insurrection, whose rallying-places were the high-lying towns of Manresa, Cardona, Berga, and Solsona. Only three practicable roads enter the valleys of the Upper Llobregat, one communicates by the line of Manresa and Vich with the Ampurdam; a second goes from Manresa via Cervera to Lerida, and ultimately to the plains of Aragon; the third is the high-road from Barcelona to Manresa, the main line of approach from the shore to the upland. But there is another route of high importance in this section of Catalonia, that which, starting from Barcelona, avoids the upper valleys, strikes inland by Igualada, crosses the main watershed between the coast and the Ebro valley below Cervera, and at that place joins the other road from Manresa and the Upper Llobregat, and continues on its way to Lerida and the plains of Aragon. This, passing the mountains at the point of least resistance, forms the great trunk-road from Barcelona to Madrid. [Illustration: Catalonia.] The third region of the principality is the coastland of Tarragona, a district cut off from the coastland of Barcelona by a well-marked cross-ridge, which runs down from the mountains to the sea, and reaches the latter near the mouth of the Llobregat. The communication between the two maritime districts is by two roads, one passing the cross-ridge by the defile of Ordal, the other hugging the beach and finding its way between the hills and the water’s edge by Villanueva de Sitjas. The coastland of Tarragona is not drained by a single river of considerable volume, like the Llobregat, but by a number of small streams such as the Francoli and the Gaya, running parallel to each other and at right angles to the coast. Each is separated from the next by a line of hills of moderate height. The southern limit of this region is the Ebro, whose lower course is protected by the strong fortress of Tortosa. Its main line of internal communication is the great coast-route from Barcelona to Tarragona, and from Tarragona to the mouth of the Ebro. Its touch with Aragon and Central Spain is maintained by a good road from Tarragona by Montblanch to Lerida.