The Ottoman Public Debt Administration (OPDA), was a European-controlled organization that was established in 1881 to collect the payments which the Ottoman Empire owed to European companies in the Ottoman public debt. The OPDA became a vast, essentially independent, bureaucracy within the Ottoman bureaucracy, run by the creditors: Its governing council included one representative each from British, French, German, Austrian, Italian, Dutch, and Ottoman creditors, and one representative from the Ottoman state. It employed 5,000 officials who collected taxes that were then turned over to the European creditors. At its peak it had 9,000 employees, more than the empire's finance ministry.
The Istanbul High School building was originally constructed as the Ottoman Public Debt Administration (OPDA) headquarters.