We don’t allow buildings like skyscrapers (modern types of buildings) higher than 40m. The height limit of a building can reach up to 90m (in a case of a castle or palace on the ground).
( this rule is only for the ground – this particular rule is NOT valid on skyboxes, which you may have any type of building no matter what the height. )
Do not place a skybox on the ground... Skyboxes are for the sky.