India, June 19 -- The silent, secretive tunnel-like corridor crawls through facing rows of darkened cells. The underground place is truly a revelation.

This is one of the most puzzling segments of Tughlakabad Fort. In fact, the entire 14th century citadel, here in the southern tip of Delhi, is a kind of puzzle.

The fort is huge, yet sits somewhat detached from mainstream Delhi-so unlike the equally splendid Red Fort. That monument, further north, commands a dynamic presence in the capital's public life. Red Fort hosts the Prime Minister on Independence Day, and poets on Republic Day. Teeming with tourists, it is permeated with the story of Mughals, whose legends have seeped into the most minute crevices of our popular culture.

But Tugh...