Any places that is a "must see" in Lewis?

I assume you mean Lewis in the Outer Hebrides? If so, it is a beautiful island, with some fantastic scenery, amazing beaches and interesting history.

You must visit the atmospheric Callanais Stones, at sunset if you can, and there are other stone circles in the area too. There are also several reconstructed houses and villages, it is interesting to see how little the basic structure had changed between the old iron ige huts at Bostadh and the blackhouses that were still lived in in the last couple of centuries. The Lewis web site has an interactive map of some of these sites.

http://www.isle-of-lewis.com/
http://www.visithebrides.com/

Also don't miss driving round Harris, if you possibly can. The scenery is magnificent. We drove down the western side, passing huge sandy beaches, then back round the eastern side. Be warned, driving is very slow, especialy on the eastern roads. Partly because of the narrow, winding, single track roads (very little traffic) but mainly because I had to stop the car every 2 minutes to admire the view and take another picture of another pretty loch, fishing harbour, seals on the rocks, etc.

Thank you very much you've been very helpful

I thought you were talking to me!!!
8-)

If you haven't booked any accommodation and want to stay somewhere really different, why not stay in a traditional blackhouse? We just visited the museum there but I think it would be a lovely place to stay.

http://www.gearrannan.com/

I was told some find it amusing to find there is a place called the Butt of Lewis...

http://www.islandsofinspiration.com/butt_of_lewis.htm

some beautiful photographs, enjoy...

Also dont miss the broch a few miles north of Callanais.Is it Dun Carloway?