Modifiers are great for building a model, but perhaps you are wondering if you can use more than just one modifier. Well, of course, you can! Keep reading, because here is an easy example of how to edit a Mesh Object with multiple modifiers!
You can start with a realistic object, for example, a Greek column, and don’t worry: you can use the default cube to start modeling it. Remember to press Tab on your keyboard to switch to Edit Mode, set the bottom of the figure just above the X axis so you can edit it better, then make it thinner by pressing G and dragging.
Once you have it, Subdivide the flat cube, go to the Orthographic view to see the whole square, and delete the faces at the top and that one on the left-hand so that you will have only the right corner cube aligned to the origin point.
Now you can add the Mirror Modifier, set the mirror at the X and Y axis to re-complete the whole square, and turn on the Clipping Option. After having that, you must create an Inset and Extrude up the figure.
Note: Notice that the Inset Tool, by default, has a boundary set, which means that when you use it, the inset will be created just in the middle. To put this out, you need to go to the bottom left-hand popup at the corner and enable the Boundary option or press the shortcut for the Insert Tool (Hitting I on your keyboard) and then press B.
You can use the Inset and the Extrude Tool as often as you want to create the base of the column you wish to. Afterward, once you have it, you can add a cylinder and set it until you think the size fits the base. Then, as you did with the square, maintain only the right corner of the cylinder so the Mirror Modifier can re-complete it.
Note: If you want to make it more realistic, add some Loop Cuts and Bevels and extrude out the base of the figure to build a more complex shape. Don't forget to smooth it.
Once you have it, and if you still have ridged edges, you can go to the Edge Selection menu, right-click, and select the "Clear Sharp" option. Also, that is going to help you to smooth the figure.
There you have it! Now you can add a second Mirror Modifier on the cylinder (because this will reflect that base just above your model). But be careful, remember that the mirror modifier operates according to the location of the origin point, so you need to set it just at the top center, so when you choose the Z axis, the mirror modifier can properly reflect it.
Reminder: The order in how you organize the Modifier Panel affects your model.
If you want to reflect the base you did before, you can also use a second Mirror Modifier and flip it based on the pivot point of a second object. To do that, check if the Origin Point is in the center of the cylinder and go to the Mirror Modifier Panel, and with an eyedropper, select the cylinder, and that's it!
You can add more details if you want, and if you're going to make more columns, you need to join the whole figure. After that, you can add the Array Modifier, so you won’t need to duplicate it several times.
