Ground is not flat where it should be

Hi @kuntal_750, welcome to the community!

It’s possible that some regions on Cesium World Terrain are outdated due to the older height data. There are some suggestions on this other forum thread here:

You could also try using the From Ellipsoid option on Cesium3DTileset to build on a smooth ellipsoidal surface. However, this does smooth out the entire Earth, so it will look less realistic from afar.