I am making a cake for my brother's 40th birthday and I would like one of the tiers to have a cityscape as in this picture (but actually a mix of Sydney, Paris and London on the one tier). How does one do this? Does it require a Sillhouette/Cricut? 

I am assuming that it is made from either modelling chocolate or strengthened fondant?

Any help will be so very gratefully received,

Amelia

If you can draw one freehand then make yourself a template and cut it out of fondant. You can find cityscape images online if you need some inspiration! 

I find modeling choc gives you more detail as its a bit stiffer and if you roll it out then place it on a large tile or stone/glass cutting board that's been in the freezer for an hour you'll find it easier to cut as you'll get less 'tugging' from the knife :-)

Ooh, great suggestion! I used modelling chocolate on the weekend for the first time in the hope that it would give me a nice hard result but mine kept sagging in the hot weather we've been having. I never thought to work on a cold surface.

The level of detail in cutting, and getting them straight, scares me. I wonder if one could use a Sillouette/Cricut thingamy?

To use a Sillouette or Cricut (would need old version of SCAL or Fairy Cuts etc to use this machine) you would need to find an image that you liked and then convert it in the appropriate program so that the machine would cut it but it should be doable.
 

Buy the Craftsy class by Lauren Kitchen "Intro to Modeling Chocolate" - she creates a cityscape-type cake in this class.  No electronic cutter used - just templates and an Exacto knife. 
 

I took that Craftsy Class. IT will help you a lot as to the Cricut, I believe, it takes some time to get the hang of it. I don't think you will be able to get it and then come home, plug it in and be ready to go IMHO