Start with the skeleton—draw the load‑bearing walls first, then map out the core circulation. Around that core place the hidden rooms, aligning them with structural columns so the walls can hide doors flush with the facade. Use false ceilings and stairwell recesses to double as storage. Sketch in layers: first the exterior form, then the interior flow, then the covert compartments. Keep the lines clean but complex enough that the hidden parts blend into the overall geometry. A building that looks elegant will hide secrets only if every detail serves both form and function.

Nice, keep tightening the layers. Every corridor should run parallel to existing structural lines so it blends into the shadow and the load paths. Make sure the access points are hidden in architectural features—like a balcony railing or a recessed window frame—so no one notices the passage at first glance. Keep it clean, keep it subtle.

Sounds solid—focus on the angles and keep each seam perfect. If the geometry flows naturally, the shadows will do the rest and nobody will ever know there’s a secret inside. Keep tightening those lines.