Adding decorations to terrain generated by perlin noise?

So I am working on an terrain generator game and I was wondering if I could add decorations to the generated terrain like trees and houses and stuff like that. The terrain is like Minecraft, it's voxel and the decorations have to be voxel too. Here's my current script:

local mapsize = 250
local seed = 1500
local size = 4

for x = 0, mapsize do
    for y = 0, mapsize do
        local h = math.round(math.noise(x / 50 or 0, y / 50 or 0, seed) * 20) * size
        local p = Instance.new("Part")

        p.Position = Vector3.new(x * size, h, y * size)
        p.Anchored = true
        p.Size = Vector3.new(size, size, size)
        p.TopSurface = Enum.SurfaceType.Smooth
        p.BottomSurface = Enum.SurfaceType.Smooth
        p.Material = Enum.Material.Grass
        p.BrickColor = BrickColor.new("Bright green")
        p.Parent = workspace

        if p.Position.Y < 0 then
            p.Material = Enum.Material.Salt
            p.BrickColor = BrickColor.new("Cool yellow")
        end
    end
end

local w = Instance.new("Part")
w.Anchored = true
w.TopSurface = Enum.SurfaceType.Smooth
w.BottomSurface = Enum.SurfaceType.Smooth
w.Material = Enum.Material.Glass
w.Size = Vector3.new(mapsize * 5, 30, mapsize * 5)
w.Position = Vector3.new(((mapsize + 1) * 5)/2, -20, ((mapsize + 1) * 5)/2)
w.CanCollide = false
w.Transparency = 0.5
w.BrickColor = BrickColor.new("Electric blue")
w.Parent = workspace

If you know how to make it that it generates decorations and houses on the terrain and not on side of hills so the blocks are not floating then thank you!

• Also how to make it also generate caves?