As Alan Marcus points out, there main issue here is noise, the best way to get rid of that is via image stacking. If you take 25 similarly exposed pictures, align them and then take the average then you reduce the noise by a factor of 5. Note that aligning is necessary even if all the pictures are taken on a tripod and remote control is used, after every shutter movement there will be tiny shift in camera orientation, enough to cause unsharpness at the pixel level). Here the noise reduction should be set to off, except the long exposure noise reduction which performs a dark frame subtraction.
Noise reduction eliminates not just the noise but all the invisible details that are hidden well below the noise floor. Taking the average of the 25 pictures will then not make these details emerge. Noise reduction should therefore be applied only after the averaging over the image stack is carried out.
The noise in each individual picture can be greatly reduced by exposing for longer, but that would overexpose the brighter areas. You can deal with this problem by taking a few different exposures and compile a HDR picture. You can e.g. take ten 30 seconds exposure at ISO 100 for the dark areas. The noise after averaging and adjusting the exposure here will be approximately ten times lower than in your picture (3 times longer exposure reduces the noise by a factor of 3, and averaging over ten images reduces the noise by a another factor of sqrt(10)). You can take ten exposures at 5 seconds exposure time, ten more at 1 second, ten more at 0.2 seconds etc. etc. until you get exposures that will correctly expose the brightest lights.
In total you may then need to take, say, 70 pictures, but this doesn't take a lot more effort than just taking a few picture. The end result will be a noise free HDR picture. While correctly exposed bright areas may not be the main goal, overexposed windows and lights in the picture cause so-called blooming effects where the charge in overexposed pixels leak to neighboring pixels. Dark areas directly adjacent to bright areas then become bright, the details there will get lost.