Sorry matey, as most of the people here have already stated - what you're after is a fair bit of work, and although there may be some people around who are happy just making prefabs to order, I odn't think I've seen many of them around - most of the prefabs on the vault are parts of projects or PW's put up for other people to use.
What some of the other builders are saying above goes for me too though - although you may not be able to find a prefab that exactly fits what you're after, starting with one that's at least got some of the elements you want & moving stuff around / adding / deleting things as you need is an absolute massive time saver.
Its hard to appreciate how long it takes to set up the basic landscape, textures & layout of an area, especially an urban environment with all the associated mix of placeables, textures, effects, etc. unless you've made one or two.
The town I used as my initial starting area - "Hochoch" - in the link in my sig. was a prefab which fairly well matches what you're asking for - castle on hill, lots of buildings, big lake that you could convert into a sea by dropping the mountains on the far side & deleting all the placeables on them - then you could add in the bits that are missing - the arena etc., and maybe re-tint the houses (I really didn't like the original colours used by the builder) & you've saved yourself a load of time.
Personally I found it really hard to remember what all the different buildings etc. looked like, but Smorpheus' Toolset Index is absolutely awesome for giving you categorised pictures of all the placeables available, creatures, items, etc. that makes finding exactly what building, or placeable you want MUCH easier than otherwise - here's the link -
nwvault.ign.com/View.php You may suck at some aspects of the toolset, but once you've got a base area, playing with the tools in the terrain tab & putting in your own placeables may get you a lot further than you expect

And we're here to help you if you get stuck with any specific elements along the way.
Good luck!
Cly.