The Rumelihisarı neighborhood where Perili Köşk stands takes its name from the Rumeli Fortress, the massive fifteenth-century fortification built by Mehmed II in 1452 — the year before the conquest of Constantinople — to control the Bosphorus at its narrowest point. The mansion rises a few hundred meters from those ancient walls, on the same European shore, with the strait flowing past below and the Fatih Sultan Mehmet Bridge visible in the near distance.

At this point the Bosphorus is among its narrowest and most dramatic: the current runs strong, the Asian shore is close enough to see clearly, and the passage of tankers, ferries, and cargo ships through the strait is constant. For a building designed to impress — and the nine-floor, 5,000-square-meter Yusuf Ziya Pasha Mansion was certainly designed to impress — the location was well chosen. The problem was completion.

The building was constructed in 1911, but the story of why its upper floors remained empty for so long is not fully documented in the sources. What is documented is the result: a substantial, castle-like structure sitting on one of the most expensive stretches of waterfront in Istanbul with its lower and upper floors inhabited and its middle floors sealed, unused, slowly acquiring a reputation. Buildings do not need to be genuinely haunted to feel that way. Incompletion is its own form of atmosphere.

The mansion changed hands and purposes over the decades. In 1993 it was bought by the philanthropist businessman Basri Erdoğan. The exterior was then carefully restored and completed — in line with the original design — between 1995 and 2000 by architect Hakan Kıran, who also renovated the interior. The building that emerged from that project looked, at last, as it had been intended to look when it was built more than eighty years earlier.

In May 2002, Borusan Holding — a Turkish industrial conglomerate with operations spanning steel, logistics, automotive, music, and the arts — took a 25-year lease on the property and established its headquarters there. The choice of the Perili Köşk as a corporate address was not simply practical. Borusan had an existing commitment to arts and culture that would eventually reshape what the building is known for.

In September 2011, Borusan opened Borusan Contemporary, an art museum occupying the building alongside the company offices. The museum presents contemporary art in a space that is itself architecturally distinctive — a Victorian-inflected red brick tower on the Bosphorus, stained glass intact, with views across the water that no purpose-built gallery could replicate. The combination of corporate headquarters and art museum in a single historic building on prime waterfront is unusual. At the Perili Köşk, it works in part because the building's whole history has been about the gap between what a space appears to be and what it actually is.

Borusan Contemporary runs temporary exhibitions, and the building now appears on architecture lists and cultural itineraries. It is accessible on weekends, when the offices are closed and the museum is open to visitors who make the trip up the Bosphorus to Rumelihisarı by ferry or road. Standing outside and looking up at the red brick facade — the turrets and the tall windows, the stained glass catching light from the strait — it is easy to see why the neighborhood gave it the name it did.

The haunting, if there ever was one, came from potential unfulfilled: a building of obvious ambition sitting incomplete, floors empty, waiting for something that had not yet arrived. What arrived, eventually, was restoration and purpose. The name Perili Köşk remains anyway, a reminder that a building's history is not only what happened inside it but also what people imagined about it during the years they could not get in.