Over the next few days, I hear some grumbling that the Old City is not as clean as it once was, that there's too much peeling paint and construction dust. Yet it's hard to imagine a more beautifully preserved and lovely walled colonial city. The blue ocean against the marble tombstones at the Santa Maria Magdalena de Pazzis cemetery, the rows of town houses with neoclassical balconies—even a bad photographer can make a good showing here. If San Juaneros didn't walk their terriers and poodles on the grass along the city walls, it might seem too staged or Disneyesque.

At the crossroads of the Caribbean, on the eastern edge of the Greater Antilles, the island was spotted by Columbus on his second voyage. A lieutenant on that trip, restless Juan Ponce de León returned in 1508 to claim the island for Spain, and settled his family and troops in a mosquito-ridden swamp near San Juan Bay (then known as Puerto Rico—later, the names switched, and Puerto Rico became the island and San Juan the city). In 1519, with Ponce de León away elsewhere exploring, his family picked up and moved to a rocky, almost treeless islet at the mouth of the bay, with no freshwater and poor soil but with a strong ocean breeze that deterred insects. On his return, Ponce de León declared it a terrible location. (Or perhaps it was the betrayal that stung.) He left, so they say, before spending a night. But even without the gobernador's blessing, the settlement grew and thrived.

English buccaneers tormented the place through the 1500s, and then the Dutch burned it down in 1625, persuading the Spanish crown to fortify its strategic possession. For the next two hundred some years, the Spanish treasury nearly bankrupted itself paying for city walls more impressive than any in Spain at the time. More than one hundred feet high in spots, layered with brick, sand, and limestone, the finished walls ran more than three miles, completely enclosing the city. There were five entrance gates, only one of which remains. The small cylindrical sentinel posts that punctuate the walls became the signature of the island. From the ocean, the Old City looks like a big gray birthday cake—huge angled walls topped by a layer of brightly painted, colonnaded buildings. These walls, encircling the Old City and two strategically placed military castles, kept the Spanish flag flying high over San Juan for almost four centuries, until the U.S. Navy came around in 1898.

We don't dwell on the Spanish-American War much at home, but it's still very much on the minds of those living here, and it is the reason that Puerto Rico and Guantánamo Bay are under U.S. control. "It was like your current war," a San Juanero tells me and my husband, who'd flown down to join me for the weekend. "It too started with a misrepresentation." The battleship Maine blew up on a February night in 1898 in Havana's harbor; two months later, the United States decided it had been attacked and declared war on Spain (most historians now believe the ship's coal stores had imploded). U.S. Navy ships off Puerto Rico sent cannonballs into the side of Castillo de San Cristóbal and the three-story military barracks on Norzagaray, damaging several apartments. The Spanish fleet arrived but, resigned to their impending defeat, didn't put up much of a fight. Then it was over. Cuba received independence, and Puerto Rico, with its sugarcane fields, was brought under U.S. protection.