Reportedly a Nosferatu spy discovered the location of Alamut sometime during the Anarch Revolt. This discovery was part of the reason the Assamites chose to surrender and submit to the Tremere curse, rather than allow outsiders to attack and invade their home.
The exact number of vampires in residence at Alamut is unknown. Due to the secrecy involved and the large amount of blood needed by sorcerors, it is likely Alamut has a resident human and ghoul population to keep the Assamites fed. Even with a resident herd, it is unlikely that Alamut could have more than a few dozen Assamites in residence at a time and still remain undiscovered.
The layout of Alamut is also largely unknown. Only a few details have surfaced.
The Central Vault is a large open area within Alamut, carved out of the living rock of the mountain. Looking up into the vault will reveal the night sky... despite being underground. The vault does not open to the actual outside, but somehow mysteriously allows viewing of the stars. The stars shift through the seasons, mirroring the outside world. Whether the stars are visible even during the day is unknown.
The Black Throne of Haqim allegedly rose out of the ground when Haqim drove his spear into the solid rock. He built Alamut around it. The spear is still embedded in the throne. Several prophecies about Gehenna mention Caine ruling from a Black Throne. It is unknown if this is the same throne.
The Heartsblood of the clan is a great magical well filled with vitae from all the Assamites that have ever visited Alamut. The primary use for the well is to allow sorcerors to use sorcery on their clanmates. A ritual allows them to draw a sample of a specific vampire's vitae from the well, which may be used to affect them with sorcery from afar. It is believed ur-Shulgi used the Heartsblood as a focus for breaking the Tremere curse on the clan.