Every year around this time, a small group of preservationists in Honolulu rally together to try to save a ruin of architectural history that's as improbable as it is beautiful: the Waikiki Natatorium, a massive Beaux Arts swimming pool that has been sitting in the ocean along the south shore of Oahu for the past 87 years.

Yes, there's an Olympic sized swimming pool built into the Pacific Ocean. The pool, framed from the shore by an enormous decorative arched entryway, was built to honor the memory of World War I veterans. The entryway is a well-known landmark. Locals gather there to swim at a small beach adjacent to the structure, and to barbecue in the grass nearby. But the pool itself has been closed since 1979, and the debate over what to do about it—raze or preserve—has become a sort of microcosm of Hawaii politics, one of those perennial issues that brings up larger cultural questions about land use and the fundamental values of a place.

Saving the pool would be costly in perpetuity; the ocean is constantly eating away at it. Destroying the pool would be both expensive and environmentally risky. But then there's the question of history.

What should we save anyway?

And what do we lose when we destroy a piece of the past?

Modernity is a reliable antagonist to preservation. The promise of efficiency—primarily of cost and space—is what tore down New York City's Penn Station, the classic example of a demolition decision that never should have been made. And it's easy to see that the once-grand train station—replaced with the depressing underground lair we know today—belonged to the same era as the Waikiki Natatorium:

The old Penn Station opened in 1910 and was torn down in 1963. Incidentally, that was the year that many officials in Hawaii started pushing for demolition of the swimming pool war memorial. Half a century later, most of those officials have died, but the Natatorium remains.