Pokemon Legends: Arceus takes place in the past of Pokemon Diamond and Pearl, in the area that will one day become the Sinnoh region. So it's naturally full of connections to Diamond and Pearl, including story threads, characters, native Pokemon, and of course its map.
It would have been easy for Game Freak to take some liberties here, but the map of Hisui you explore in Legends is surprisingly accurate to the Sinnoh we know from the fourth generation of Pokemon games, right down to where towns are in relation to one another and some of the geography in each area. And even if you're not looking hard, you can find lots of obvious references.
Spoilers for Pokemon Legends: Arceus' map locations below:
The most obvious starting point for a little map exploration is Jubilife Village, which obviously will become Jubilife City in Diamond and Pearl. It's surrounded on two sides by the Obsidian Fieldlands.
Zooming in on Obsidian Fieldlands puts the Sandgem Flats to the south of Jubilife, where Sandgem Town will eventually be, with Lake Verity in between.
There's no corresponding location for Twinleaf Town, sadly, but you can imagine it would be on the far south coast of Sandgem Flats.
Ramanas Island is roughly where Ramanas Park (or Pal Park) is, though it's not really an island anymore by Diamond and Pearl.
To the north are the Floaro Gardens, which have a large flower patch in the center where Shaymin can be encountered later. This seems to line up with Floaroma Town, though it's forgivably a bit off where it would be in Diamond and Pearl in relation to Jubilife.
Then to the east, still in the Fieldlands, you can find Oreburrow Tunnel, right about where Oreburgh City (or its associated mine, more likely) will end up.
The other areas of the map don't have quite the same extreme level of close correspondance, but there's still plenty to be found. In the Crimson Mirelands, the Unown-filled Solaceon Ruins seem a bit off in relation to other landmarks, but it's still easy to see how the future Solaceon Town ended up built around them.
It's mostly off due to its relationship with Lake Valor, which is to the north in Legends rather than its normal place to the southeast in Diamond and Pearl. But we'll forgive them this one.
You can also find Spiritomb's dwelling in the same very rough area, though again it's thrown off a bit by the location of the other two.
Cobalt Coastland is also pretty tricky to find 1:1 comparisons to, though the Veilstone Cape is exactly right next to where Veilstone City will eventually be.
And Firespit Island could easily be the beginnings of Stark Mountain in the post-game Diamond and Pearl Survival Area, with Heatran found in both.