The Venetian Hotel lobby & Canal are amazing. Walk along the canal and see all the shops plus have the lighting change from day to night. You can also see the living statues preform. they have restraunts along the canel that make you feel like you are dining in Venice.
http://www.venetian.com/

Go to old downtown Los Vegas (Fremont St) during the day and the strip at night for a real contrast in atmoshphere.

Prepare not to sleep LOL