I want to know the answer to the following question:
At the start of 15th century, the biggest Byzantine city was what?
All the background I'm provided with is that "By the beginning of the 15th century, the Ottoman advance meant that Byzantine territory in Greece was limited mainly to its then-largest city, Thessaloniki, and the Peloponnese (Despotate of the Morea).". Is that enough to answer the question?