10 A river flowed out of Eden to water the garden, and there it divided and became four rivers.
19 Now out of the ground the Lord God had formed every beast of the field and every bird of the heavens and brought them to the man to see what he would call them. And whatever the man called every living creature, that was its name. 20 The man gave names to all livestock and to the birds of the heavens and to every beast of the field.
24 He drove out the man, and at the east of the garden of Eden he placed the cherubim and a flaming sword that turned every way to guard the way to the tree of life.
Before I get to the main point, this post is only relevant to Christians who believe there was predation before the Fall. I'd like to reiterate an observation I've made before: the definition of young-earth creationism typically includes three planks: age of the universe about 6-10K years old; Noah's flood was a worldwide event; no animal death (predation, parasitism) before the Fall. However, these tenets are logically independent of each other. You could affirm one, two, or all three. If you affirm just two, there are three different ways you could pair them off.
The description of the garden raises intriguing questions about how we should visualize the setting. What keeps tame animals inside the garden? What keeps them from leaving the garden? What keeps dangerous animals out of the garden? Likewise, posting guards at the eastern end or edge or side of the garden implies some sort of barrier around the garden. It had one entrance or exit.
Perhaps the garden was situated in a narrow river valley with sheer escarpments forming a natural barrier. Maybe there was a waterfall downstream. Maybe the river emerged upstream through a rocky opening. Or maybe it was a subterranean river that surfaced in the garden. Maybe there was an interstice on the eastern side, permitting ingress or egress.
Another possibility: the garden was located on a fluvial island. In that event the river would form a natural barrier on all sides. Perhaps there was a rope bridge connecting the island to the mainland.
On a related issue, although the garden animals were tame, that doesn't necessarily mean them were harmless. It may only mean they were tame in relation to Adam and Eve. But tame animals like tame lions, bears, and honey badgers can still be ferocious in relation to other animals. In theory, the garden might have predatory animals that guarded the garden from incursion by wild animals that might be dangerous to humans. On that scenario, the garden might be less physically isolated from the surrounding wilderness.