What interesting things are there between Barstow and Vegas along Rt 5?

Besides Calico, the world's tallest thermometer is in Baker. There are also several gas stations there for a pee break. That is about it until you get to Primm aka Stateline where Buffalo Bills has a really big roller coaster. Also note that I-15 between Barstow and Pri,, has a death rate about 3 times the state average on a lane mile basis. Because you are outside the "golden hour" for medical evacuation if you have a serious crash. Drive carefully.

Ooo, Flower makes an appearance and gets the smackdown! Welcome back.

Yeah, that's I-15 that takes you to Vegas.

As for anything to do between Barstow and Vegas, stopping at Primm/Stateline is about it. If you want outlets, you could have stopped at the outlets in Barstow. IMO, there's really nothing to do except drive as fast as possible. Nothing but a straight line of desert.

Neither I-5 nor I-10 will get you to Las Vegas. You are looking for I-15 from Barstow to Vegas.

As for anything interesting. Most people on that road are on that road for one reason to go to/from Las Vegas from Southern California. There is a reason for this. Except for a defunct water park you can see off of the side and the worlds biggest thermometer there isn't a whole lot.

If you are into shopping at all we often stop at the outlets in Primm(AKA State Line for the "Old School" people). It is your basic Outlet mall but there are a couple of stores we usually don't get to. At the very least it is a good Pit Stop for a few minutes.

If you are a bit adventurous and it is open you can try out the Desperado Roller Coaster in Buffalo Bills Casino.

Nothing BUT geological features, folds, anticline, synclines, faults, etc.

It's I-15 and the only thing on it are the CHiPs officers waiting to give you a ticket for being 25+ mph over posted

You dont take I-5 to Las Vegas from Barstow. You take I-10.

EDIT: YES, I goofed up. I havent been to So Cal for years I forgot. It IS I-15. Sorry