What is the significance of the Kaaba in Islam to Muslims?

The Kaaba is the Qibla or prayer direction of Muslims worldwide. Tradition has it that it is the first house built for the purpose of worship and was constructed by Adam initally, then later rebuild by Abraham and Ishmael. It was severely damaged through floods and rebuilt once more during the time of prophet Muhammad. The Kaaba is the destination for the Muslim pilgrimage (Hajj), which is obligatory for every Muslim at least once, and thus all Muslims on the globe, past and present connect with each other.