Why was mecca an important city for the arabs on the arabian oenninsula

Do you mean any specific times?

Basically, it has been a place for worship for a long time. Right now (and for many centuries) it has been the center of Islamic faith, but even before it was a center of the previous pagan religion.

In the Islamic faith, the most important place is the Kaaba, or the Black Stone in it, which is believed to originate from God.