Every year, millions of Muslims gather to perform the Hajj in the Saudi Arabian city of Mecca, where the city's Grand Mosque overflows with pilgrims as many more clamour for space outside the mosque's walls.

It's a reality that Saudi authorities are hoping to change with an ambitious expansion and renovation project that is under way across the city.

But expanding and renovating the Grand Mosque and the city’s infrastructure will be a challenge to do without disrupting what Muslims believe to be the holiest of spiritual journeys.

Al Jazeera's Ayman Mohyeldin takes a look at some of the plans.