I never realized that there are two Civil-War-era cemeteries in Marietta – one Confederate, and one Union (I thought there was just one, for both). What turns out to have been the Confederate one I had seen before, but I could not get in this time, because it was closed. The cemetery’s website claims that this is for the sake of maintenance, but the police officer stationed near the main entrance told me that there had been some recent vandalism in the cemetery, which suggests that the closure as much for prevention of damage as for repair of it. So these photos are the best I can do.
I’ll take the liberty of reposting Wikipedia’s photo of the historical marker.

Wikipedia
Note how the cannon was returned in 1910. Apparently the Arch of Tribute in the second photo above was put up in 1911. Two data points in the first blip.

Google maps.
Marietta National Cemetery, by contrast, is open – and better maintained by the Department of Veterans’ Affairs. You can find it about a half mile to the northeast of the Confederate Cemetery.
A marker tells where it came from.
More on Henry Green Cole, “the most dangerous man in Georgia,” can be read at Marietta Patch. Cole is lucky not to have shared the fate of James J. Andrews of the eponymous raid.
One interesting feature of this cemetery is the appearance of an older design for the headstones featuring a shield, which is different from today’s. (The slightly bluer-colored headstones to the left in the photo are examples of the newer format.)
Marietta National Cemetery is full and has no more space for interments. Since 2006, military burials have taken place in the Georgia National Cemetery in Canton, of which there have already been several thousand. I stopped by for the first time earlier this summer. The current format of the headstones allows for the discreet expression of some individual identity at the top. Most have a Christian cross. I guess there is no longer any need for the Confederate emblem, but if you’re not Christian, or a particular type of Christian, or not religious at all, plenty of other options are available from the VA. Spotting them as they appear in the cemetery is fun. Some examples:

Native American Church of North America.

Lutheran Church – Missouri Synod.

Church of Jesus Christ of Latter-Day Saints.

The Community of Christ (formerly the Reorganized Church of Jesus Christ of Latter-Day Saints).

Sufism Reoriented (founded by Meher Baba).