Hi everyone, long time lurker, first time poster. First of all, I should congratulate you all on your fantastic maps, I am blown away every time I visit.

Now onto my question. Does anyone have any techniques for mapping complex 3d cities or structures. I am developing a setting on my blog The City In Darkness and I want to start mapping it.

Here's the header
Bathed in eternal darkness, the City in Darkness hangs impossibly in a plane of complete nothingness. Flickering light from thousands of lanterns and torches illuminates what one could only describe as a huge rock suspended in space. The top of this rock is covered in closely huddled buildings that aim ever higher at an empty sky
The city is a mishmash of buildings, tunnels, streets, all built on top of one another. I am thinking perhaps some kind of 3d modelling might be necessary to map it but all the programs I tried don't seem appropriate (mostly architectural modelling tools).

Does anyone have any suggestions,

thanks!