Reflective floor?

I want to make reflective a marble floor, but i don’t understand how can I do this.
I tried to use Reflection Probe but doesn’t work very well on plane meshes… same story for Cubemap.
Could someone give me some advice?

Use an appropriate shader, such as this one:

Shader "Custom/MirrorReflection"
{
	Properties
	{
		_MainTex ("Base (RGB)", 2D) = "white" {}
		[HideInInspector] _ReflectionTex ("", 2D) = "white" {}
	}
	SubShader
	{
		Tags { "RenderType"="Opaque" }
		LOD 100
 
		Pass {
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			#include "UnityCG.cginc"
			struct v2f
			{
				float2 uv : TEXCOORD0;
				float4 refl : TEXCOORD1;
				float4 pos : SV_POSITION;
			};
			float4 _MainTex_ST;
			v2f vert(float4 pos : POSITION, float2 uv : TEXCOORD0)
			{
				v2f o;
				o.pos = mul (UNITY_MATRIX_MVP, pos);
				o.uv = TRANSFORM_TEX(uv, _MainTex);
				o.refl = ComputeScreenPos (o.pos);
				return o;
			}
			sampler2D _MainTex;
			sampler2D _ReflectionTex;
			fixed4 frag(v2f i) : SV_Target
			{
				fixed4 tex = tex2D(_MainTex, i.uv);
				fixed4 refl = tex2Dproj(_ReflectionTex, UNITY_PROJ_COORD(i.refl));
				return tex * refl;
			}
			ENDCG
	    }
	}
}