Given the choice between an hour at an underground luxury spa and a good baked potato, what hungry traveler wouldn’t opt for the spud? As it turns out, a recent tuberous marvel served on a rooftop with a view of the Acropolis was not baked but rather chargrilled, and it did wipe a 20-euro bill and change from my pocket. (Europeans don’t tip, but I do.) More on the potato will follow, because unpacking a most singular setting should come first. 

While they may not realize, all those who enter the lobby of the Hotel Grande Bretagne are privy to a palimpsest of Grecian hours past. As one of Europe’s grand hotels and a point of reference on the frenetic map of modern Athens, it is more than simply a place to stay — and in fact I’ve never had that pleasure. It has anchored the northeast corner of Syntagma Square, roughly opposite the Hellenic Parliament, since 1874. It was the first electrically powered hotel in Greece. 

In October 1940 the guests had to get going when the hotel became headquarters for the king, the government, the army general staff, and Allied forces, but in April 1941 the invading Germans commandeered it after entering Athens. With the liberation of Greece in October 1944, the Grande Bretagne became the seat of the interim government and British forces. On a visit to Athens the following year, Winston Churchill, who had done much to try to calm the local waters in turbulent times, received a hero’s welcome close to the hotel’s entrance. 

One summer day in 1969 my mother, on a quick visit from Izmir, observed Jacqueline Kennedy Onassis having a quiet lunch with her second husband, Aristotle Onassis, in the lobby restaurant — yes, the hotel that is fulcrum for the political life of a nation is also a perennial celebrity magnet, and the list of illustrious guests is long. 

With Syntagma Square as the hotel’s front porch, when demonstrations are afoot there, sometimes the attendant commotion cannot be avoided. On a foggy day in February, ahead of an appointment for a sports massage at the renowned GB Spa, I was supposed to meet my friend Foutzopoulous in the lobby café. But Greek artistic workers were clamoring for better pay in the square, traffic was blocked, and he was going to be late. That’s when I repaired to the GB Roof Garden, a restaurant with a major league view and, as it turns out, a quietly cool menu.

It is also one that instantly dispels the notion that all Greek food is simple. Some of the best Greek cooking does happen to be quite uncomplicated, but pops of creativity turn up where one least expects them, such as in the GB kitchen’s alchemical sleight of hand with a potato that comes from Naxos, the largest island in the Cycladic archipelago.

The menu describes it as a “chargrilled Naxos potato with ‘beurre noisette’, cauliflower purée with fermented leek and Naxian graviera sauce.” Graviera is a kind of Greek cheese that resembles gruyère and beurre noisette, as far as I can decipher it, is a kind of (very tasty) hazelnut butter. 

Years ago in the print pages of this newspaper I wrote with little hyperbole that it was worth crossing the Atlantic for the chocolate almond croissant of Parisian baker Ladurée. Now, with similar conviction, I can say it is worth traversing the Mediterranean for a go at this flavorful, gussied-up spud. Not only is it visually arresting, with dollops of green suggestive of spring, but it is delectable, too: a boldly earthy creation yet with a surprising soupçon of sweetness.

Is there something slightly frivolous about a potato that comes with this price tag? Certainly,  but it is also the price of admission to some unique theater. At the table behind me sat a Japanese family of three, the father aiming his Nikon zoom lens at the Parthenon while his toddler son polished off a plate of spaghetti. Next to their spot the chief rabbi of Athens noshed with two friends. A table or two away, a smartly dressed waiter listened calmly as a lady-who-lunches type complained that her fish tasted too fishy. 

In short, it was the kind of mix not easily found in a tourist café or most hotels these days. That cosmopolitan perfume flows all the way down to the spa, a cavernous space one level below the lobby replete with gym and lavish swimming pool. There is also, in addition to a traditional sauna, an Herbal Steam Bath that uses Greek-grown herbs, an Amethyst Grotto for a revitalizing eucalyptus-infused lift, and a Laconium sauna for — well, I’m not sure for what, but they were all too hot for me to linger long.

The spa’s sports massage, which I hoped might tame a stubbornly sore shoulder, was great though, and lasted about 45 minutes. Every so often I felt a faint rumble and I knew that, tuber-fortified as I was, it wasn’t coming from me. It was just the Athens Metro, rolling along several feet below this zone of elevated languor in the center of everything.

Unpacked is a new, periodic travel column from Mr. Grant in which he highlights or otherwise deconstructs a destination or experience of potential interest to today’s curious traveler.