I picture would help. Did yours not load?

Whoops. Fixed. Thanks!

i would just put it above the lock where you would normally place the dead bolt...if someone really wants to break into your house, they are going to, no matter what (our house was under renovation and recently broken into to take some tools the contractors left...we have a similar door and they just kicked it in even with double dead bolts, one where you would normally put one and one towards the top...the door frame splintered and they walked right in but didn't even touch the glass). i LOVE your door by the way!

don't worry about them breaking the glass unless you are known to have a collection of something expensive/illegal/interesting in your house. mostly out in the sticks you get door rattle-ers.... if the door is unlocked they come in and help themselves, if its locked they move on to the next house. as long as your house is harder to get into than the next house you'll be fine.

keep first floor windows closed at night unless you have a thingy that keeps them from getting raised, and ditto on second floor windows that are easy to shimmy up a porch to get to.

I placed mine about knee-level on a similar vintage door. It works fine and at least appears to be a challenge to reach.

Double cylinder dead bolt.

How about a security system?

P.S. I originally thought about a double-cylinder (keyed both sides) deadbolt, but then I realized that I'd have to leave the key in while I was at home - in case of emergency - and it's really unlikely that I'd remember to take it in and out, so I'd rather have a thumblatch instead so my family can get out safely in the event of fire, etc. Plus, whenever it had the key in it, it might as well be a thumblatch, so it's a thumblatch.

We have a double cylinder deadbolt in our door. I hung a nail on the side of the door trim and hung the key there for quick access.

Yeah, I'd been warned that the double-cylinder thing was dangerous and inconvenient. Originally I had even hoped to install an electronic deadbolt for keyless access.

Here's an idea: What if I went against everyone's opinion and got a new modern door - with a peephole. What would people's recommendations be?

If it helps? I was told when I was buying a full glass door that robbers don't break the glass, they push the door in and break the jamb. Maybe breaking the glass is a movie thing?

You should do what helps you sleep at night. That's a beautiful door, but if your worried about break ins get a solid door with a peep hole. The electronic dead bolt sounds cool too, especially when your hands are full.

I have a sliding glass door and did not feel that the latch was secure enough. My contractor installed a bolt that attaches to the slider and goes down into the floor. There are two holes. The second one allows us to open the door a few inches and still have it bolted into place.
In your case, that would be hard for someone to reach, and also not a likely place for someone to look for a lock. Yours would have to have a somewhat different set up because yours is not a slider. Our bolt can be released and locked with one's foot.

My slider came with the above posted foot lock. Not sure it would be appropriate for the OPs type of door.