What are three ways constantinople's location was beneficial to the byzantine empire ?

Attacking Constantinople by sea was difficult. The strong currents of the Bosporus endangered hostile fleets without shelter. Meanwhile the Golden Horn served as a perfect harbour for the Byzantines in war and peace. During times of war, it sheltered friendly ships. At the same time it allowed Constantinople to receive supplies by sea to withstand long sieges. 

The only landward route to the city lay on its western side. Countless hosts of bloodthirsty enemies approached from this front in the hopes of taking the city. But the land walls of Constantinople continually thwarted their efforts until 1453. In 1453, the Ottomans, relying heavily on gunpowder and cannons managed to breach the ancient walls and overwhelmed the defenders.

it is a : ) always outside of government control