10 hours stop-over at Frankfurt Main Airport... What to do?

How far is the city from the airport/ how long is the train ride? Any nice places I can visit that are close by? Is transportation expensive? Also, I don't speak German, so do most people speak English? If I get out of the airport I can leave my checked in luggage in the airport right? I have always... show more How far is the city from the airport/ how long is the train ride?
Any nice places I can visit that are close by?

Is transportation expensive? Also, I don't speak German, so do most people speak English?

If I get out of the airport I can leave my checked in luggage in the airport right?
I have always flown non-stop before, so I actually don't know how connecting flights work in terms of checked in luggage.

Oh... I am flying through Frankfurt because it was the cheapest flight to Ireland. And my Aunt was paying for the ticket. Long layover time though.. but it would be worth it if I am able to go around in Frankfurt for a while, even just to take pictures.

Thanks again!
Update: Thanks for all the answers so far.

I have a US passport- flying from California.

I arrive at Frankfurt 10:15 am then my flight to Ireland is at 8pm...

What are other famous spots? I want to take many pictures. =)

Thanks for all the info again! Your suggestions are making me excited!!! =)
Update 2: I will be there near end of May... How's the weather like?

thanks!
Update 3: Thank you so much for all the detailed answers!!! =) I found out through here that there is tour offered. Has anyone tried that? Would you recommend it? Or would it be better to just tour by myself? I thought this would be nice since there is one offered at 14.15h ( which is 2:15pm right? hehe) so I would have... show more Thank you so much for all the detailed answers!!! =)

I found out through here that there is tour offered. Has anyone tried that? Would you recommend it? Or would it be better to just tour by myself? I thought this would be nice since there is one offered at 14.15h ( which is 2:15pm right? hehe) so I would have time to explore/ eat by myself for a couple of hours (11-2pm) then go on the tour.

t_maia20, Bojan:
Are those places mentioned in the tour near the Main square in Roemer? I wouldn't want to pay if they are just there and I can see them myself.
I am planning to take your advice and take the Metro to Roemer (there is no train stop there?)
will also buy the Frankfurt card..
Apparently, there is also tour office in Romer, is that close to the Main square? That way, I would have to go back to the Main train station.

Thanks again!!! =)

Also

http://www.frankfurt-tourismus.de/cms/tourismussuite/en/sightseeing_frankfurt_rhine_main/guided_city_tour_frankfurt.html
Update 4: How far is Romer main square from Main train station?
thanks!
Update 5: Thanks for all the help!!!

I really appreciate it!!! =)
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