Once upon a time, I had a favorite restaurant in Rome.

This restaurant wasn't five-star. It wasn't fancy. But it was everything you'd want from a Roman trattoria: Good, fresh dishes, particularly the pastas; dad cooking in the back, kids serving out front; convenient location (a stone's-throw from the Forum!); moderate prices; checkered tablecloths.

Sadly, this is also everything tourists, understandably, would want from a Roman trattoria. And where the tourists go, the quality flees — at least here in Rome.

It's a sad story. But it's not a unique one.

In fact, you see it again and again in Rome: A place becomes a local favorite. Then someone writes it up. Then it winds up in a guidebook. Then, just as the deluge of tourists really starts, once the place has really made it, once you'd think the owners might work all the harder to maintain that success and re-invest and be creative… that's exactly when the quality slumps. The cooks change. The servers get surlier. The food gets worse. And the prices go up.

I never thought I'd say this about the restaurant that, even a year ago, made me wax poetic about truffle ragu and eggplant, the one where I took every single guest who visited, the one I could count on to be easy on the palate and (almost) as easy on the wallet. But Taverna dei Fori Imperiali has, it seems, taken the same path as countless Roman restaurants before it.

The seeds of demise probably were planted back in 2006, when Frank Bruni wrote it up in a glowing restaurant review for the New York Times. (A "real find," he wrote). The taverna started doing so well that it changed locations, moving into a tonier and bigger spot (like the old place, right across from the Forum). Other reviewers started writing it up, too, including myself — I included it as a pick for lunch my article for the Guardian last summer, "Eat Like a Local in Rome." When that article came out, the food was still great, the price still good, and the place was still packed nightly with lots of tables of Italians. (Almost always a good sign).

But over the next few months, the menu changed. The prices rose; no longer was I shelling out 25 euros for a dinner, but 30. Thirty-five. I could understand that — hey, the place was getting popular — but the pastas, usually so delicious, seemed to lack a certain something. Still, I had to give them credit: I never saw the restaurant without Dad cooking in the back, either his son and daughter serving clients themselves, just like always.

In the meantime, the restaurant climbed to nearly the top of Tripadvisor. That's when things really seemed to change.

So, after a couple more mediocre meals there, I went back again last week. It was one last shot. I still felt like I could almost taste that first ragu I'd had here. Trust me when I say it was a taste worth fighting for.

It was lunchtime. There wasn't a single table of Italians. While the son was in the restaurant, we were served mainly by waiters I didn't recognize; the daughter was nowhere to be seen. And Dad? He was still there. But, in all my meals there, it was the first time I'd ever seen him in "civilian clothes," without his chef's hat. Nor did I see him enter the kitchen once throughout our entire meal.

Needless to say, not having the same cook, the one who before had seemed so proud of making his creations personally, is a big change. And, of course, chefs don't remain chefs forever. They train new cooks. They move on. They retire. It's understandable.

But here's the thing: This was a change we could taste. And it wasn't good.

My companion and I ordered a starter of liver patè. The patè was fine… the toast it was slathered on, burnt. The cost? Eight euros.

Well, on to the pastas, always Taverna's fortè. Portions seemed to have shrunk. The main menu's puttanesca (9 euros) was fine, but nothing particularly special. I had a carbonara that was served lukewarm, salty, and seemed to be swimming in liquid — uncooked egg? Fantastic. Not the worst food, or even the worst carbonara, that I've had. But definitely not great, especially for 13 euros.

The bill — which came with a receipt only when we asked, and not with a smile — with water, no wine, came to about 18 euros each. Not terrible. But not worth it.

(And let me just say it kills me to write that. Oh, Taverna! How I once loved you! How I wish I still could!)

It's a sad tale. But I share it because it's also a cautionary tale. And I think we can all learn from what it tells us: If you're visiting Rome and trying to figure out the best local places to eat, don't rely on TripAdvisor, don't rely on guidebooks, and don't even rely on articles written more than 6 months ago. As even Anthony Bourdain said in his "No Reservations" Rome episode, to "out" a restaurant as being good, to expose its brilliance to the masses, is to kill it.

And in Rome, that happens quickly. So quickly that you have to let go of that memory of aromatic, delicious, heartstrings-pulling ragu… and go in search of a new favorite restaurant to replace it.

(Anyone have suggestions?)

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