Needing lens for travelling with Nikon d90?

I'm moving to London (from Australia) for 1-2 years to do a lot of travelling. I've got a Nikon d90 and would like to buy and take just 1 lens with me that will be great for traveller photos. I'll need something with a good zoom range and i want a decent quality as i want to come back with amazing photos.

Currently i have the 2 standard lens' that come with the kit which haven't been the best.

Any advice would be greatly appreciated: D

Added (1). @delhiguy i didn't say that the kit lens' are bad, i'm just saying that i'd like to buy 1 good one to save on space. It would be great to keep the comments positive and helpful - thanks.

You did'nt like kit lens because it was kit lenses.

well. Because you are moving from Australia to London, you can buy any expensive lens. Atleast it will give you mentally satisfaction that you have bought expensive lenses.

Give me 10 points.

The 18-105mm is reputed to have very good sharpness through its range, and pretty good versatility.
The versatility of the Nikon 18-200mm is hard to beat in a single lens. Stopped down to about f9, sharpness is mostly very good, although often below the 18-105mm in parts of its range. The cheaper non-Nikon 18-200mm lens are reputed to be not as good.

I use a Nikon 18-200mm lens with my D90 for traveling. As with all other super-zoom lenses, it is not the greatest lens as it loses sharpness under f/8. However, at f/8 it compares with my other lenses for sharpness.

For that reason (using it at f/8), it is pretty much a daylight-only lens. But I'm willing to exchange the limitation of using it in daylight vs. The convenience of only needing to take one lens on vacation.

Here is a webpage showing a comparison in sharpness between the Nikon 18-200mm vs. The Nikon 18-55mm and 55-200mm lenses:

http://www.althephoto.com/lenses/super-zooms.php

And I agree with the above statement that I would avoid the less-expensive non-Nikon brands. Even though the Nikon lens is not perfect, it is as good as it gets for super-zoom lenses.

Probably the Nikon 18-200mm would be your best bet. I have one on my D300 & it's a reasonable 'all rounder'.It's not as sharp as my primes, but it's good enough for most things.

18-105 would be a good lens with a capable zoom for sure and low price. But I would recommend also trying out/ buying a prime lens. A 50mm 1.8 or 1.4 for example. It may have a narrower field of view but photos come out with really good color rendition and quality. It is good for low light and is light weight, but you won't be able to take wide angle though but its a compromise for the really nice photos it takes.