curious if anyone knows when the straights gave way and the Mediterranean basin flooded???

See 73:7.1

73:3.1 "a long narrow peninsula—almost an island—projecting westward from the eastern shores of the Mediterranean Sea."
73:3.3 (823.3) This Mediterranean peninsula had a salubrious climate and an equable temperature; this stabilized weather was due to the encircling mountains and to the fact that this area was virtually an island in an inland sea. While it rained copiously on the surrounding highlands, it seldom rained in Eden proper. But each night, from the extensive network of artificial irrigation channels, a “mist would go up” to refresh the vegetation of the Garden.
I believe you have shown this accurately.

74:6.1 The Adamic family grounds embraced a little over five square miles. Immediately surrounding this homesite, provision had been made for the care of more than three hundred thousand of the pure-line offspring. But only the first unit of the projected buildings was ever constructed.

73:3.4 (823.4) The coast line of this land mass was considerably elevated, and the neck connecting with the mainland was only twenty-seven miles wide at the narrowest point. The great river that watered the Garden came down from the higher lands of the peninsula and flowed east through the peninsular neck to the mainland and thence across the lowlands of Mesopotamia to the sea beyond. It was fed by four tributaries which took origin in the coastal hills of the Edenic peninsula, and these are the “four heads” of the river which “went out of Eden,” and which later became confused with the branches of the rivers surrounding the second garden.
The question is about whether the hills of Eden peninsula of Urantia extended along the westward coastal area. I believe that if it is true that there were hills along this region, then the structure of the tributaries would appear differently, except in the eastern section of your diagram. Especially I think that two of the tributaries would originate from a more central northerly and southerly locality.

73:3.5-6The dominant idea was to be the glorification of horticulture and the exaltation of agriculture.
The site chosen for the Garden was probably the most beautiful spot of its kind in all the world, and the climate was then ideal. Nowhere else was there a location which could have lent itself so perfectly to becoming such a paradise of botanic expression. In this rendezvous the cream of the civilization of Urantia was forgathering. Without and beyond, the world lay in darkness, ignorance, and savagery. Eden was the one bright spot on Urantia; it was naturally a dream of loveliness, and it soon became a poem of exquisite and perfected landscape glory.

73:4.3 A zoological garden was created by building a smaller wall just outside the main wall; the intervening space, occupied by all manner of wild beasts, served as an additional defense against hostile attacks. This menagerie was organized in twelve grand divisions, and walled paths led between these groups to the twelve gates of the Garden, the river and its adjacent pastures occupying the central area.
In your diagram you show that these 12 divisions are stacked in long East-West sections, whereas I had imagined them as being stacked in long North-South sections. I do not see evidence to agree with your perspective here., so I am offering a second perspective.

73:5.5 By the time of Adam’s arrival most of the plants of that section of the world were growing in Eden. Already had many of the fruits, cereals, and nuts been greatly improved. Many modern vegetables and cereals were first cultivated here, but scores of varieties of food plants were subsequently lost to the world.
Would it be possible that some of these seeds or clonable plant material, exists preserved in the ruins of Eden?

73:5.2 At the time of Adam’s arrival, though the Garden was only one-fourth finished, it had thousands of miles of irrigation ditches and more than twelve thousand miles of paved paths and roads. There were a trifle over five thousand brick buildings in the various sectors, and the trees and plants were almost beyond number. Seven was the largest number of houses composing any one cluster in the park. And though the structures of the Garden were simple, they were most artistic. The roads and paths were well built, and the landscaping was exquisite.
It would be difficult to imagine the concourse of these infrastructures. I accept that you have ommitted these detail from your diagram. However let us imagine that these paths were suited from the resources of the land, perhaps of fine simple cobblery.

Rick, thank you...very nice graphic. It's good to be able to visualize this place, which must have been magnificent.

MaryJo

One feature of that original Garden that I always liked was its use of the zoological area that restricted the wild beasts and used them as a defense against invaders...a very wise thing to do! And what a difference from how we conserve these beasts today - the few that are left, that is.

Here in Colorado, there is a nature preserve out on the eastern plains in Keenesburg: "A 9793 acre refuge for more than 500 Lions, Tigers, Bears, Wolves and other rescued large carnivores..." On this preserve, the humans are allowed to visit via a raised walkway that allows the animals to be observed - but the animals are not caged. Rather, the visitor walkway IS caged. Other zoos are, to me, very sad examples of the wrong way to conserve this kind of wildlife...I like how, in the Garden, they still could be free - relatively.

Just a little tidbit of info inspired by your map...I wonder how many acres comprised the Garden's "zoo?"

Thanks again, Rick...

There is not much to elaborate. The circumstances seem to imply the type of resources available to the Amadonite colony. Stones & Trees, and various types of Mud or Mortar. These were the resources they used to build, combined with a degree of precision and ingenuity. The cultivation implies growth of plants which would later fuse into some of the structures, or be used as renewable construction material. What would it require, for the irrigation system to live up to the hype of the sanitary regulations of this city? It would have to be separated channels for fresh water and perhaps the waste would run into the river. The Roman Civilization exemplifies the type of cobblery and stone-laying necessary to maintain such infrastructure as irrigations. I have no real imagination of the place you are trying to depict. When I try to imagine it, I think of glowing crystals inside the earth, that enhance the chemistry of the soils, and a real connection between the life of the land and humanity. 12,000 miles must have been condensed into an intricate network, with a few stone-arched bridges. Then there is the overgrowth of the fruitful things that were not mentioned as growing in the garden of Eden in the Bible. The truth is that 15% cultivation is a promising figure for any city-state with the intention of self-sufficiency. Many of the additional paths would be part of the garden design itself: demarcating the sections where one species of nuts grows, from sunny meadows. There were spaces perhaps where the growth intentionally promoted the gathering of birds. And also the fandors existed during those times. You can imagine that the best scientists of botany would have analysed the interaction between plant-propagation, and bird migratory and dietary behaviour. This promotes the theory that in such salubrius climate, what the Urantia Book considers full cultivation would rate as the highest yield potential by the modern standards. Much of the land would be dense forest, and much of the fruit may have had to have fallen down before it was gathered. I think that full cultivation implies that all of the available dirt has been connected to the roots of plants, and that those plants were intentionally planted or left to stand.

The coastal mountains would be like one long ridge, with a steep slope on the outside and a gradual slope on the inside, perhaps of a crescent moon shaped, with 50kmx40km elliptoidindal shaping.

73:4.3 A zoological garden was created by building a smaller wall just outside the main wall; the intervening space, occupied by all manner of wild beasts, served as an additional defense against hostile attacks. This menagerie was organized in twelve grand divisions, and walled paths led between these groups to the twelve gates of the Garden, the river and its adjacent pastures occupying the central area.
In your diagram you show that these 12 divisions are stacked in long East-West sections, whereas I had imagined them as being stacked in long North-South sections. I do not see evidence to agree with your perspective here., so I am offering a second perspective.

I imagine that the 12 grand divisions were not laid out in block fashion but conform to some extent to the random, irregular effect of the mentioned menagerie.