The answer is RIYADH, six letters. No second candidate exists here, so this joins the small set of geography entries with exactly one correct fill. If six squares do not match your grid, the problem is either a miscount or a misread country, and the second half of this page covers what else the clue might be asking.
One city, one spelling, six squares
Names transliterated from Arabic often reach English in several forms, which is a real hazard in crosswords. This one is not a hazard. Puzzles use RIYADH, six letters, and the spelling is stable across American and British grids alike.
The letters are worth noting for crossing purposes. The Y sits in the middle rather than at the end, which is unusual and makes any crossing entry through the third square very informative. The final H is likewise a strong constraint, because relatively few down entries end there. Confirm either of those and the rest of the word tends to fall in on its own.

An interior capital, not a coastal one
Riyadh sits well inland, on the plateau of the Najd in the middle of the country, rather than on either coast. For solving purposes that inland position is the fact worth carrying, because every Saudi city an American reader can name off the top of their head sits somewhere else. The name itself is connected to the Arabic word for gardens, which points at the oases that supported settlement there long before oil money rebuilt the place.
The old core still shows what it grew from. The Masmak fortress, a squat clay and mud brick building with round corner towers, sits in the historic center surrounded by a city that now runs to millions of people and a skyline of towers. Very few capitals hold that contrast inside a single neighborhood.
If six squares do not fit, check the country
Most failures on this clue are not spelling failures. They come from reading the clue quickly and answering for the wrong country, since the region has a dense cluster of capitals that crossword grids all use.
| Letters | Capital | Country |
|---|---|---|
| 4 | DOHA | Qatar |
| 5 | AMMAN | Jordan |
| 5 | SANAA | Yemen |
| 6 | RIYADH | Saudi Arabia |
| 6 | MANAMA | Bahrain |
| 6 | MUSCAT | Oman |
| 7 | BAGHDAD | Iraq |
| 8 | ABUDHABI | United Arab Emirates |
| 10 | KUWAITCITY | Kuwait |
Two of those are worth holding in memory. DOHA is the shortest capital in the region and therefore the one editors reach for in tight corners. ABUDHABI catches people out constantly, because Dubai is the better known city and is not the capital of anything.
The Saudi cities that are not the capital
Jeddah is the major port on the Red Sea coast and the arrival point for pilgrims heading inland, which gave it an international character the capital took longer to acquire. Foreign embassies operated from Jeddah for years before relocating to Riyadh, a piece of history that occasionally shows up in a trivia styled clue.
Mecca and Medina are the holy cities, both in the western part of the country, and neither has ever been the political capital. Dammam anchors the Eastern Province near the oil fields on the Gulf side. A clue naming any of those cities is not asking about government, so if your grid is fighting you, reread which word the clue actually emphasized.
Reading the clue from the other direction
Constructors clue this entry in both directions and the reverse form is easier to misjudge. RIYADH may be defined by country, by region, by the Najd, or simply as a Middle Eastern capital, and any of those still wants the same six letters.
The one variation to expect is a clue that asks for the country rather than the city. Saudi Arabia is too long for most slots, so editors use SAUDI on its own, five letters, or the older ARABIA, six. Both are standard entries, and ARABIA shares a square count with RIYADH, which is exactly the kind of overlap a Saturday grid enjoys. When a six letter geography entry refuses every crossing, test whether the clue wanted the country rather than its capital.