Each year millions from around the world make the pilgrimage to Mecca, the birthplace of the prophet Muhammad and the holiest city in Islam. And soon a hotel of massive proportions will be constructed to house many of them.

Designed by consulting firm Dar Al-Handasah, the reportedly 10,000-room Abraj Kudai will be the largest in the world by room count-far surpassing the current title holder, the 6,198-room MGM Grand in Las Vegas.

The $3.5 billion hotel will be built in the Manafia area of Mecca’s central zone. In addition to the hotel, the 645,830-square-foot complex includes a shopping mall, restaurants, helipads, a bus station, and a convention center.

The Abraj Kudai is just one project in a slew of modern constructions in Mecca.

With such rapid expansion, some worry about the preservation of city’s historical architecture. For instance, in 2002, the 18th-century Ajyad Fortress was demolished to make way for the Makkah Royal Clock Tower hotel, a 1,972-foot behemoth.

Despite concern, construction continues in Mecca-the Abraj Kudai is scheduled to open in 2017.