Lands have indefinite period of use / life. All other assets wear and tear and eventually cease to exist. But you can not destroy a piece of land. If you acquire some land along with buildings, you will have to separate the land value from the total cost. You might want to consider the market value of the land in the vicinity.
Note IAS 16.58 says "Land and buildings are separable assets and are accounted for separately, even when they are acquired together. With some exceptions, such as quarries and sites used for landfill, land has an unlimited useful life and therefore is not depreciated. Buildings have a limited useful life and therefore are depreciable assets. An increase in the value of the land on which a building stands does not affect the determination of the depreciable amount of the building"
