Ha ha fence

Thought this was interesting
https://www.permaculturereflections.com/the-ha-ha-fence-alternative/

This is an old English garden technique.
It allows one to keep deer and sherp,etc off of the shrubbery without a fence spoiling the veiw.
I believe one side is generally higher than the other.

I was wondering if it would work for deer

A haha has the main intent of keeping the animals of a landscaped park (sheep, cattle, deer) from encroaching on the gardens around the house, yet keep the appearance of a continuous lawn stretching from the house into the far distance.  So there's a ditch rather than a raised feature like a fence, and the far slope of the ditch (away from the house) is gentle and grassed.  The near side is always a vertical wall, high enough that the animals won't try to jump it.  You'll get the dimensions by looking at the real ones around grand houses in England (which mostly have deer parks), that have been found to work.  Google 'haha ditch' and click 'images'.
Here, for example:

Might work for deer if you had a straight vertical wall 7 ft tall. Cheaper method might be an electric fence, depending on what you are trying to keep the deer from.

This photo shows a deer ha-ha as it's being used NOW for a deer park.  Maybe it's the slopes, but the deer won't cross.  In other places, yes - the fences are 8 feet tall, or the deer will cross - especially rutting stags!  They're fallow deer, by the way.

I saw the lovely remains of a ha ha in a country house hotel we were celebrating a family anniversary in a year or so ago. The house and croquet lawn on the left, the (former) animal parkland on the right.
A big investment in labour to gain the perfect view, however this ha ha is about 150 years old and would still function over the remaining length.

Cool technique! I've seen references to this, but never understood what a ha-ha was... Don't think they've ever been used in my part of the world.

How wide is the ditch? Two meters or so? Just wondering if it would keep roe deer out. They can jump really far.

From memory the wall here is about 6 foot tall, so maybe 2m+ wide. Maybe it would have been deeper originally. It probably depends on what livestock they were grazing in the parkland, but that could have included red deer. We certainly find that the sheep are less likely to jump a fence up hill than one that is below the road: I'm thinking a ditch could be used strategically with a fence to make it more of a barrier.