To be clear, it is currently really easy to find because major earthworks are being done, and that requires space to move in the equipment to do it, along with new roads to get to points that were previously inaccessible, being the middle of nowhere.

To see what it will look like afterwards, try to find High Speed 1, aka the Channel Tunnel Rail Link, now that it's had nearly 20 years to be landscaped and vegetation to grow back. If you don't know what you're looking for, you won't see it.