The Chantry stands in the heart of Sales. The gothic tower is home to the order in New Babylon. It is not exactly a secret. Any Kindred with some skill could trace the Chantry. Getting in or attacking it is another story considering it is across the road from the main Police Precinct of Sales. The Masquerade is of utmost importance. Open to members of the Covenant only. Speculation about the heresy that happens here is riff.
The Chantry is one of the most heavily guarded towers. High level Security including drones protect the Libraries and ritual chambers of its members.