Real properties as objects of property rights are certain land areas which are among themselves divided with geometrical lines (cadastral and building plots) and everything what is at their surface or under it being affixed by man’s work. A legal presumption of legal unity of real property, which is expressed by the traditional principle superficies solo cedit, is a permanent bond between objects affixed to land, permanent buildings and other structures as well as everything what is generated by a soil at its surface, either being self-grown or sown, that is, planted. Modern legal systems are familiar with the institute of legal duality of a land and a building (right to build, right of superficies etc.), and some of them with the legal duality of a land and a tree. Therefore, the legal unity of real property is only a rebuttable presumption (praesumptio iuris tantum). The building plots (real properties) as objects of the right of ownership and other property rights are horizontally bordered with other real properties being owned by a certain person, or with a common good or public good in common use. The real properties are vertically bordered by the border of owner’s legally justified interest to exclude interventions of others in depth and height. Out of these borders a common good has been spread and it can be used by everyone according to conditions and in a manner prescribed by the state within its sovereignty limits. The idea according to which the ownership right is unlimited and reaches the stars (usquae ad sidera) was stroked down by an aeroplane as it happened with the idea on unlimited state sovereignty in air traffic which was stroked down by Soviet Sputnjik. The right of ownership over land can be limited by the right to build, however, the object of the right to build as a real property in legal sense does not suppress the object of the right of ownership, rather it only limits owner’s titles. In the same area there is the object of the right of ownership and the object of the right to build.