Nearby localities include Kaff al-Jaa and Masyaf to the east, Wadi al-'Uyun and al-Shaykh Badr to the south, Hammam Wasel, al-Qamsiyah and Maten al-Sahel to the southwest, Taanita to the west, al-Annazeh to the northwest and Deir Mama to the northeast.

It is situated just east of the Mediterranean coast and its ruined castle stands on a plateau roughly 850 metres (2,790 feet) above sea level and just above the town.

[3] Al-Qadmus is home to an important medieval castle that served as the headquarters of the Isma'ili community in Syria, known as the Assassins during the Crusader era.

[10] When North African scholar Ibn Battuta visited al-Qadmus in 1355, during Mamluk rule, noting that it was part of the niyabah ("governorship") of Masyaf, a dependency of Tripoli.

[12] In 1683, during the Ottoman period, Muslim scholar Abd al-Ghani al-Nabulsi visited al-Qadmus and noted the emir of the fortress belonged to the Tanukhi clan, an Arab tribe that originally settled in the Batanea area of southern Syria during Byzantine rule and migrated northwards.

[16] Pressure from the surrounding Alawite heartland caused many to emigrate for Salamiyah, although the town maintained its political and economic significance in the region and served a commanding role in the central Coastal Mountain Range, similar to that played by Safita.

The town was a destination for farmers from al-Annazah, Talin and al-Shaykh Badr and exported the agricultural products of the area to major cities like Hama, Tripoli and Beirut.

[21] Prior to the ascent of the Baathist government in 1963, the built-up areas of al-Qadmus was largely concentrated just south and east of the citadel, where most houses were built closely together.

Tourism-centered development spearheaded by private contractors began in the late 1980s, mostly concentrated north of the fortress, east of the town's main thoroughfare and south of the east-west highway.

Many in the Alawite community subsequently boycotted Ismaili-owned businesses in al-Qadmus, particularly the furniture stores and sweet shops, and instead opted to purchase from the surrounding markets.

The local Ismaili merchants were angered at the severe decrease in their business's profits as a result of the boycott and began hurling stones at Alawite-owned storefronts.

Later that evening some Alawite residents retaliated by ransacking and burning down 27 Ismaili-owned businesses, causing damage worth an estimated LS 10 million.

[22] The clashes ended when two Syrian Army battalions from nearby military bases closed the roads leading to al-Qadmus and detained and questioned about 500 suspects.