The Ancient Obelisk is a special residential building that is only obtainable by collecting fragments of the Ancient Obelisk Selection Kit, given as a time reward for finishing an Ancient Egypt Settlement within a certain amount of time.
The Ancient Obelisk Selection Kit provides a choice between a new level 1 Ancient Obelisk building or a Ancient Obelisk Upgrade Kit.
The Ancient Obelisk produces coins and gives a Defense Boost to the attacking army. When motivated, its coin production is doubled and additionally it produces forge points and on level 4 even goods.
The Ancient Obelisk can be upgraded by Ancient Obelisk Upgrade Kit item. To upgrade the Ancient Obelisk, use the Ancient Obelisk Upgrade item on the Ancient Obelisk that is already situated in your city. Its upgraded version will then be placed directly on the same spot in your city and the production timer will not be reset. Note that the upgraded building will be from your current era, even if the old one was from one of the earlier ages.