Not bad :)
but there is room for improvement:
Water color... and maybe add a flow..

There are some black lines... I like to remove them (jalonso learned me that), you can keep them exept for on the church, there are way to much black lines on there...

What are the white dots next to the water?

Try to improve your cars.. Or just delete them, like I do ;)

Change those letters...

Change those people,

try using some other colors.. Dont really know how to say that in English but I dont really like the green of the grass, the sand, moe's tavern color, the church color, the colors of the peoples, those from the brige in te park and those from the cars.. The others are mostly fine :)

WHats with that park? That tree looks very weird, white dots, stripes in the water... that pretty weird...

You made something very large.. than it will be very hard to do some detail work, and do everthing good....
I suggest you try something smaller next time, so you can put alot of time in a building, instead of that you have to rush over them... (police looks like time, hospital too, moes tavern doesnt)

Btw, I see you used a building of mine (pimped your style) in it, please give me credit and note me next time... Yes you are allowed to change it, but you are not just allowed to change it a very little bit and put it in a larger work of yours.. This time ill agree, since its very old, but next time please ask, and make shure you give credit (allways give credit to any1 who does anything)

Sorry About The "pimp my building" house,  I will remember next time

And if someone put some good colors of Grass, sand and Water I will be thanks (if I wrote something wrong, sorry im a brasilian)

I agree with lollige: you would benefit from starting on a smaller piece. This work of art shows that you need to learn the fundamentals of detail and shading in the isometric perspective, and those things, like any others, are best learned when you can give them your full attention. Try working on simpler objects to start with and remember to add detail with highlights and shadows.