We know now the Ubuntu comes with a nice interface called unity. But some of the oldest geeks may won't like this new Interface. There is a good news for them, Ubuntu can how the gnome interface by doing some simple steps.
1. Open your terminal press CTRL+T or access it from the terminal
2. execute the following commands as root user
sudo add-apt-repository ppa:gnome3-team/gnome3
sudo apt-get update
sudo apt-get install gnome-shell
3. Now restart your system. Now you will get option in the user login screen, to choose the Interface you want.
Select the Gnome Interface and enter your username and password. Now you will enter in to the Gnome Interface.