You’d expect a governor’s mansion to hold its fair share of state secrets, but discovering a sprawling, century-old bunker underneath it still comes as a shock. According to a story in the Hindustan Times, that is just what happened this week, when a British Colonial-era hideout was found beneath the Maharashtra Raj Bhavan in South Mumbai.

The bunker was unearthed after a wall that had covered the entrance was removed, a project undertaken after old employees shared rumors of tunnels beneath the complex. Sure enough, behind the temporary wall was a 20-foot-tall metal gate (topped with a gnarly spiked bar) that led down into an underground tunnel system. Upon exploring the old bunker, they found that it covered around 5,000 square feet underground, split up among hallways and 13 separate rooms. Many of the rooms were marked with faded wooden signs indicating a shell store, a cartridge store, and a workshop, among others.

With systems to provide the bunker with fresh water and air, it seems like it would have been a self-sufficient munitions store as well as a defensive position. Having been abandoned after India’s British rulers left the country, officials were worried that they might encounter snakes, or other hazards in the depths, but the remarkably preserved shelter didn’t even seem to have a single bug living in it.

Maharashtra governor Ch Vidyasagar Rao is now trying to locate experts that can help preserve the abandoned bunker as a cultural heritage spot.