The visitor may prolong his excursion to the ruins of O’Hara’s Tower, above Europa Point. It was built by Governor O’Hara as a belvedere, and forms a picturesque object. Thence, the descent of the eastern side of the Rock is accomplished by a staircase known as “the Mediterranean Steps,” which winds and bends and twists around precipice after precipice, and from point to point, with the Rock above and the blue expanse of the Mediterranean below. The silence and solitude of the spot produce a deep impression on the mind, which seems to enter here into an intimate communion with Nature. We forget the works of man and the purpose for which the grim Rock is so stoutly held; when, on turning a sudden angle, we see, at the [Illustration: O’HARA’S TOWER ON THE SUGAR-LOAF. _Page 130._ ] extremity of a small platform, and in a situation inaccessible if not invisible from below, a solitary but formidable gun, commanding Catalan Bay and the Neutral Ground. At a short distance is another, but of less calibre. This singular recess is known as the Mediterranean Battery. * * * * * So much for the Rock itself. Let us now invite the reader to accompany us on an excursion to Carteia. We pass through the Lower Lines, which to the unmilitary eye appear absolutely impregnable, and enter upon the sandy isthmus of the Neutral Ground. A survey of the works at this point of access to the mainland convinces us that the Spaniards are justified in calling it the _Boca del Fuego_, or “Mouth of Fire.” The narrow causeway which crosses the artificial morass can be blown away at once by the fortress guns. But even if an enemy overcame this obstacle, he would find himself confronted by a line of strong batteries, stretching from the foot of the Rock to the sea, and at the same time exposed to the cross-fire of three or four rows of guns, placed in tiers along that side of the precipice. As we continue our way along the Neutral Ground, we observe that military science has done its utmost to render it impassable by a hostile force. Willis’s Batteries are planted on a bold crag, half-way up the Rock, so as to be able to sweep the isthmus with a withering fire; and the rugged front of the Rock yawns with fissures,--_los diantes de la vieja_, or “the old lady’s teeth,”--from each of which frown the black muzzles of heavy guns; while, in addition, the Old Mole, or “Devil’s Tongue,” projects its threatening mass into the sea.