SEE THE WHOLE WORLD
Render distances of 256+ chunks. Cities and mountains on the horizon.
Distant Horizons is a level of detail mod: it renders simplified terrain far beyond normal render distance at low performance cost, 256+ chunks. Watchtowers actually watch over something, and you can see nations' skylines from far away. It works with player-built structures, and with shaders through Iris when the shader supports it.
The server provides a prebuilt Distant Horizons file so the world is already scanned for you. Grab it from the modpack page and drop it in as described there. Without it, the mod still works, you just have to explore before distant terrain appears.