The architect was Mario Palanti, an Italian who shared his client's devotion to Dante Alighieri, and he built the structure to the exact proportions of the text. The Palacio Barolo rises 100 meters, one meter for each of the hundred cantos of the Divine Comedy. Its 22 floors divide into three realms: the basement and ground floor are hell, floors one through fourteen are purgatory, and fifteen through twenty-two are heaven. The lobby radiates from a central dome through nine vaulted archways, the nine circles of the Inferno, lined with Latin inscriptions and monstrous carved figures. On the lower floors, geometric reliefs nod to alchemical fire, the green-white-red of the Italian flag, and Masonic symbolism. Even the foundations were laid out to the golden ratio. Few buildings have ever been so completely an idea made physical.

Luis Barolo was an immigrant who reached Argentina in 1890 and grew rich in knitted fabrics, and he carried with him a particular dread about the Old World. He believed Europe was beginning to drift toward collapse, and he wanted Dante's remains carried as far from the continent as possible, safe in a tower at the bottom of the Americas. The poet's ashes never made the journey, but the conviction shaped everything. Palanti was designing a near-identical sibling at the same time across the river in Montevideo, the Palacio Salvo, the two towers conceived as a matched pair. When the Barolo opened in 1923 it was the tallest building not only in Buenos Aires but in all of South America, and it held that title until the Kavanagh Building overtook it in 1935.

Crown the building and you reach its most ambitious flourish. At the summit sits a powerful rotating beacon, bright enough to be seen across the Río de la Plata in Montevideo, more than two hundred kilometers away. In Dante's scheme it represents the nine choirs of angels and the divine light at the end of the pilgrim's ascent. But Palanti intended something grander still. The beam from the Barolo and the beam from its twin, the Salvo, were meant to arc toward each other across the estuary, a pair of welcoming pillars greeting travelers arriving from the Atlantic, an echo of the Pillars of Hercules. Through some miscalculation, the two beams never quite met over the water. The gesture failed, but the ambition behind it tells you everything about the men who dreamed this place.

The tower keeps one final secret for a single night each year. A small ornamental spire at the very top is shaped to evoke the Southern Cross, the constellation that wheels over the southern hemisphere, and it is set so that it aligns with the actual stars of the Cross on the ninth of July, Argentine Independence Day. Today the building has shed its mythic ambitions and filled with ordinary working life: lawyers' offices, a Spanish-language school for foreigners, a shop selling tango clothes, the studios of architects and designers. Declared a national historic monument in 1997, it still runs its original, gloriously antiquated elevators. Visitors climb through hell and purgatory to reach the beacon, and the city of Buenos Aires unfolds below them, exactly as Palanti meant it to.