Well...... The best answer would be Athens, but remember, Greece was not an organized country then. If you count Crete and all the islands, there are many. But back then, Athens was still an important city.
The Greek capital letter for Phi is Φ.
The Greek capital letter for Lamda is Λ.
The Greek capital letter for Xi is Ξ.
The Greek capital letter for Omega is Ω.
The Greek capital letter for Theta is Θ.
The Greek capital letter for Psi is Ψ.
The Greek capital letter for Delta is Δ.
The Greek capital letter for Sigma is Σ.
The Greek capital letter for Gamma is Γ.
The Greek capital letter for Pi is Π.
the capital of the greek eastern empire is Byzatine
In Greek capital letters, "Stavros" is spelled as ΣΤΑΥΡΟΣ.