Hebrew Cemeteries and burial question?

I've always noticed that in many Hebrew (or is it improper to say Jewish)? cemeteries, the placement of the headstones are terrifically close together.

Is there a reason for this? I've been told when i was a kid that the burial takes place with the deceased being placed in an upright position. Of course this would make sense regarding spacing but is this true and if so why not laying down flat as with cemeteries of other faiths?

Also, I might not have had the opportunity to observe and in my area but I don't see mausoleums either. Are they just lacking in my area of is this also a method not used by that faith.

I thank you for you answers in advance.