Getting to much verts when importing a model to unity

We have been working on project that includes photogrammetry. The problem that is happening
is that if we export a model from RealityCapture that is huge I mean it is not a 3D cup it is a big building and if we export it
to unity our verts start to increase immediately . We can up to 30mil vert and the game can not even start.
Is there any chance or procedure that can lower the verts in unity we have been doing everything in to lower them but haven’t succeded yet.
Best regards .

There are a lot of tools that can reduce vertices of meshes, here are some:

Thank you for that but we did the simplify in RealityCapture of the mesh and reduced it to 100.000 verts ( low polly) and we use this with our high polly (200mil poligons) and then we use this two typs of polygons (LP and HP) in Substance painter to get normal map , ambient occlusion map , high map etc… and we have 7 models with the exact same procedure ( each one has 100.000 verts) but the problem is when we import that model including the textures and UVs etc…we get 30mil verts and more and with 30mil. verts it is impossible to run VR in Unity . When we import this seven models to UnrealEngine we are working without any problems . So we like unity more because it has more potencial for our projects , and this is just a beginning from one big project so we need to solve this because if it makes problems on this building how will it be when we import much more 3D models in the same project . Best ragards .