This Tetrarchs column are made of igneous rocks, there are four of them. Dating from around 300 AD. Since the Middle Ages, it has been fixed to a corner of the facade of St. Mark's Basilica in Venice, Italy. The statues probably originally decorated the columns of the porch of the Philadelphion in Constantinople. 

This object is part of "Scan The World". Scan the World is a non-profit initiative introduced by MyMiniFactory, through which we are creating a digital archive of fully 3D printable sculptures, artworks and landmarks from across the globe for the public to access for free. Scan the World is an open source, community effort if you have interesting items around you and would like to contribute, email stw@myminifactory.com to find out how you can help.