Toronto is changing fast; a fact we can all recognize. While most of this growth is happening above ground and up into the sky, one of the most significant projects under way at this time is occurring below ground. Tunnelling is now complete for the TTC's York-Spadina Subway Extension, and the empty concrete tunnels have attracted a number of urban explorers below ground for a glimpse of what is to come. Today's Photo of the Day, submitted to the UrbanToronto Flickr Pool by Jonathan Castellino, shows a beautiful yet stark view of a tunnel's interior, as a woman walks down the tunnel away from the camera.

Walking through an under-construction subway tunnel, image by Jonathan Castellino

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