If you want to find and visit all the landmarks available in Forza Horizon 5: Hot Wheels, here is a list of all 28 of them.
Note: The "dragon landmarks" or festival site don't have markers on the map and that seems to be intentional but two other markers: The Knot Rock and The Supersonic Spiral don't have map markers either and it seems to be a bug (at least for me :-)
Bonedust PitCloud ForestDragon's FallForest FallsForest Falls Dragon
Frostbite Flame LoopGiant's CanyonHammer MountainHammer Mountain Dragon
Hot Wheels OutpostHydra GorgeHydra's RevengeIce Cauldron Dragon
Magma CanyonSupersonic SpeedwayThe CauldronThe Duo-naughtThe Forgotten GorgeThe Frozen ApostlesThe Hammer DropThe Ice CauldronThe Knot RockIt is just a guess that this landmark is located somewhere here. It is probably bugged and currently does not appear on the map, but I scored it near this location (check the screenshot).
The LookoutThe NexusThe RamThe Supersonic SpiralNo marker on the map (a bug?), but I scored it near this location (check the screenshot).
The Turbo ClefTreetop Towers