Given the task definition and input, reply with output. This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.

With Istanbul as its capital and control of lands around the Mediterranean basin, the Ottoman Empire was at the center of interactions between the Eastern and Western worlds for six centuries. Following a long period of military setbacks against European powers, the Ottoman Empire gradually declined into the late nineteenth century. The empire allied with Germany in the early 20th century, with the imperial ambition of recovering its lost territories, but it dissolved in the aftermath of World War I, leading to the emergence of the new state of Turkey in the Ottoman Anatolian heartland, as well as the creation of modern Balkan and Middle Eastern states, thus ending Turkish colonial ambitions.
What was the capital of the Ottoman empire?