Lots of different options here. Every retaining wall starts with the excavation of footing. After excavation, footing is either poured, compacted, or mono-poured with the wall. Construction cost varies greatly depending on wall finish.
Finish Options
Block Wall
This involves pouring a footing and laying a block wall over it. This can be left bare and be finished as exposed block or it can be covered in stucco or veneer. If your looking for square this is the way to go!
Poured and Sculpted
Usually a one day job. Foundation is poured with the wall. Using a proprietary ad-mix we stack the concrete around rebar. This is then carved and colored to look like natural stones.
Retaining Block
Also over compacted gravel using geo-grid layering to tie the wall into the soil behind it. Super clean look, fast install.
Dry Stacked Stone
Usually over compacted gravel. Natural Stone varies greatly in both look and costs. Both material and labor depend on the look you hope to achieve. This is usually done with out mortar, layering of geo-grid and soil holds the wall in place.