Until the middle of the 19th century, Havana, like nearly all of the capitals built by Spanish conquerors in the Western Hemisphere, was a walled city. These walls were built of coral limestone quarried along the sea front, which with exposure to the atmosphere becomes quite hard. The same engineering ability demonstrated by the builders of El Morro, Cabanas and La Punta, was evident in the 17th century wall, that had the fortress of La Punta as its starting point and ran in practically a straight line south until it reached the shores of the Bay near its southwestern terminus. These walls were about 12 feet through at the base and some 20 feet in height. Throughout the entire line was a series of salients, bastions, flanks and curtains that were dominant features in the military architecture of those times. At the top were parapets on which the garrison gathered for the defense of the City. Work on the walls began with a body of 9,000 peons in 1633 and a contribution of $20,000 in gold that was exacted by order of the Spanish Crown from the rich treasuries of Mexico in order to hurry its completion. Only two gates were constructed at first, one of these at La Punta and the other at the head of Muralla Street, which latter formed the main or principal entrance for commercial purposes. A third was afterwards opened near the corner of the old Arsenal for the convenience of people engaged in ship building at that point. Extending along the water front were gradually built continuations of this wall with coral ledges forming a solid base. These eventually closed the city on all sides. This stupendous work was not completed until 1740, and even after this date occasional additions were made for purposes of better defense. Although the Spanish treasury at that time was being filled with gold from Mexico and Peru, it would seem that the Crown was very loath to part with the money, and compelled the colonies of the Western Hemisphere to build their own defenses and to make whatever improvements they considered necessary, either from contributions levied on commerce, or with the use of slaves whose services their owners were compelled to furnish at their own expense. Up to the departure of Spain’s army from Havana in 1899, sections of the old wall, several blocks in length, extending through the heart of the city, still remained intact. These, with their salients, bastions, flanks, etc., formed an interesting landmark of the olden days, when Spanish knights clad in hauberks and hose, donned their breastplates and plumed helmets to fight against the British who besieged the city in 1763. Today only one short section remains, a picturesque remnant of the past, with its little round, dome-covered watch tower still intact. This is located just north of the Presidential palace on the crest of the green lawn that slopes away towards La Punta, about a third of a mile distant.