Grič Tunnel was built in 1943, during World War II and connected to Zagreb tunnels. Its primary purpose was to shelter civilians from frequent bombings during WWII and the Croatian War of Independence.
After all, it is a part of a network of Zagreb tunnels under the Upper Town. But the only one open to the public!
You can find the tunnel entrances as they are marked with Zagreb coat of arms. Once you look at Zagreb coat of arms on the rooftop of St. Marks Church, you will notice the underground, secret door under the castle. Symbolising the entrance to hidden Zagreb network of tunnels.
Stories and legends speak of secret underground passages all over the city. One of them speaks of the great 1880 earthquake. When it is said most of the tunnels disappeared, containing the church gold.