The Secret Passages

The network of interconnecting tunnels and passages beneath the city is a street system in its own right, enabling one who has mastered it to travel virtually anywhere in the city.

Of course. the entire network shown here is only known to a few individuals the masters of the Thieves' and Assassins' Guilds, Samrad Bevrain, and Agarat Esiassen (the latter two explained in Ch5 FFF). Perhaps an enterprising sewer man has mapped out many of them, while keeping the secret from his colleagues, or an enterprising thief has copied his master's map, but such individuals are rare.

On the other hand, there are more passages than are show here. Some of these are known to only one or two people and might simply connect one house to an other, or an apartment to a shop. Others might link into the sewer system, while their users remain unaware of the vast network all around them.