Where was Querétaro? A famous and grisly painting gave it mystique. Then somebody whispered to Gully Wells, "It's Mexico's secret jewel." And so, finally, she went ...

Sometimes a journey can be inspired by a single image, but in this particular case, it was two: one a painting, the other a photograph. The painting, by Édouard Manet, was of an execution. The palette, like the image, was grim. A group of soldiers dressed in gray were aiming their rifles, with bayonets attached, at almost point-blank range, at three men standing in front of an inky wall. Clouds of smoke obscured the blood and gore but did nothing to stop your imagination from working overtime to envisage the true horror of the scene. And true it was, because the subject was the execution of Emperor Maximilian, the Hapsburg prince who had foolishly assumed the crown of Mexico, reigned for three years, and ended up before a firing squad in Querétaro in 1867. I never forgot the painting but had no idea where or what Querétaro was. That is, until I came across a photograph of the interior patio of a Moorish-looking palace called La Casa de la Marquesa, which, I guessed quite wrongly, must be in Andalusia. But the caption clearly read Querétaro.

Most people, when I began checking, seemed to know the Maximilian story. But beyond that, nobody could add much, with the exception of an art historian who told me, in a confidential whisper, that it was "Mexico's secret Baroque jewel." And, he went on, "Very few people know about it, and even fewer go there—apart from the real cognoscenti, of course." Among whom he was numero uno, naturally. A dead emperor, a Moorish palace, a Baroque jewel . . . What's not to like? Absolutely nada, it turns out.

Querétaro is bang in the center of Mexico, about 140 miles north of Mexico City, with no trace of any significant pre-Columbian ruins. Perfect. It isn't that I don't love the Mayans and the Aztecs. I've climbed halfway up the great pyramid at Uxmal, I've read Incidents of Travel in Yucatan, the 1843 classic, while traveling in the Yucatán without any incidents, and I did once spend a week at Las Alamandas, doing nothing more useful than acquiring the perfect suntan. But those days are over, at least for me. I've decided, over the years, that the most fascinating parts of Mexico are the ones that not many people bother to go to. Ergo, no tour buses, no crowds. Or, at least only Mexican crowds, which don't count since they belong there. But, as it turned out, while I was in Querétaro I discovered two other places I'd never even heard of: Morelia and Pátzcuaro, both in Michoacán. Morelia is another colonial jewel in Mexico's sparkling tiara of towns founded with lightning speed by the Spanish in the mid sixteenth century. And Pátzcuaro, although much smaller than the other two, is fascinating because it has retained so much of the character of the Tarascans, the name the Spanish gave to the indigenous people of the region. Which leads me to another lesson I've learned during a lifetime of travel: Sometimes it is much more fun not to plan every detail of a journey before you set out. Keep your mind, and your schedule, flexible and see what happens next.