بسم الله الرحمن الرحيم
You own a plot in other city and intend to sell it after ten or fifteen years, so if you bought it with the intention of selling in the beginning then it is a business property and you will have to pay zakah on its value. However, if you did not buy it with the intention of selling rather you intended to make a house etc at the time of buying then no zakah will be wajib on this plot though now you intended to sell it later.
Allah knows Best!
Darul Uloom Deoband
This answer was collected from the official ifta website of Darul Uloom Deoband in India.