Tuwaiq in the context of "Zulfi"

Najd is a historical region of the Arabian Peninsula that includes most of the central region of Saudi Arabia. It is roughly bounded by the Hejaz region to the west, the Nafud desert in al-Jawf to the north, ad-Dahna Desert in al-Ahsa to the east, and Rub' al-Khali to the south, although its exact boundaries cannot be determined due to varying geographical and political limits throughout history.

Administratively, Najd is divided into three main regions: the Riyadh region which features Wadi Hanifa and the Tuwaiq escarpment, which houses easterly Yamama with the Saudi capital, Riyadh since 1824, and the Sudairi region, which has its capital in Majmaah. The second region, Al-Qassim, houses the fertile oases and date palm orchards spread out in the region's highlands along Wadi Rummah in central Najd with its capital in Buraidah, the second largest Najdi city, with the region historically contested by the House of Rashid to its north and the House of Saud to its east and south. The third administrative unit is northerly Ḥa'il, which features the mountains of Jabal Shammar housing the Tayy capital of Ḥa'il.

Ad-Dahna Desert is the central division of the Arabian Desert. It is a corridor of sandy terrain forming a bow-like shape that connects an-Nafud desert in the north to Rub' al-Khali desert in the south. Its length is more than 1,000 km (620 miles) bordering Twaik Mountains from the east and does not exceed 80 km (50 miles) in width. It is also considered the geographical margin separating Al-Ahsa Province of Saudi Arabia from the country's Najd region. Al-Dahna Desert is therefore the string that connects the great deserts of Saudi Arabia.

The desert is a series of seven successive deserts, separated from one another by plains. Roads pass through Al-Dahnā, linking Kuwait with Al-Zilfī and Riyadh and connecting Riyadh with Hasa.