I know this is not an "urban" development since for it to work it has to be as far away from any city as possible, but considering its huge size and engineering significance I feel it is far more appropriate for it to have a thread in this section rather than be hidden away somewhere.
Here's the wikipedia article:
The European Extremely Large Telescope (E-ELT) is a planned ground-based extremely large telescope for the optical/near-infrared range, to be built by the European Southern Observatory (ESO) on top of Cerro Armazones in the Atacama Desert of northern Chile. The design comprises a reflecting telescope with a 39.3 metre diameter segmented primary mirror, a 4.2 metre diameter secondary mirror, and will be supported by adaptive optics and multiple instruments. On 11 June 2012, the ESO Council approved The E-ELT programme to begin construction of the telescope, pending agreement with the governments of some member states. Construction work on the E-ELT site eventually started in June 2014.
Here's an article from BBC News confirming that preparation work has begun:
Mountaintop blasted to build huge telescope
The top of a 3,000m-high (10,000ft) mountain in Chile has been blown up to make way for the world's largest optical and infrared telescope.
A million tonnes of rock were blasted in order to create a level surface on which to build the European-Extremely Large Telescope (E-ELT).
And some pictures of what it is supposed to look like:
This pic is too large so I only post the link: http://upload.wikimedia.org/wikipedia/commons/1/14/Latest_Rendering_of_the_E-ELT.jpg