Radial Right-Click

With a RTS interface well known, the hope is that there is no need for any menu system at all for basic RTS commands. Move, harvest, attack, follow and drop-off are all just a matter of right click when you have a unit selected. Selection is through a left click. Scrolling is by holding your mouse to the edge of the screen or using WASD.
In keeping with the same theme the right-click menu will be just as minimal. It'll consist of icons that appear in the same manner as a context menu and will be designed radially. For the prototype version, it'll just be simply arranged box-shaped buttons but the idea is shown below:

Once the player has selected something to build then the UI shifts into building placement mode. Originally I had designed it to be a simple click and if you wanted to place multiple buildings then it was a shift click.
The shift in mentality is to have a more city-building friendly UI. In that light, placing just one building is more rare than placing multiple buildings. So shift is not required. After you place a building, the mode persists in order to allow you to place more buildings. Instead, you need to right-click in order to exit building placement mode.
Building structures in Cultura is a bit complicated versus most city-building games. Because my concept of "wood" is actually a category of goods you can collect (pine, oak etc) and I want the interface to be more friendly, I opted to follow something that is a combination of Sim City 2000 and Capitalism 2 interfaces. Basically, you go through the radial menu. First you select build. Then you select housing. Then you select tent. Now you are in building placement mode. A tent requires wood and fur/skins. In the bottom right corner a window would show up to show the various options and persists as you place buildings. Those settings are used per building placed. This allows for a quick way to build a lot of "common" structures using cheaper materials and then splurge on a select few "elite" structures in a quick and easy manner.

Sim City would have a large left panel with lots of building categories which would open into small sub-categories. Capitalism would let you place a building and then go into a settings menu. For Cultura, the large left panel is replaced by a radial context menu. The settings screen is replaced with a temporary settings panel at the bottom right of the screen. The real estate used in the UI is then temporary and once you are finished it immediately goes away.
I'll work on tweaks to make the UI experience faster/smoother once I have more of a game to play around with and see what is good and what needs to change.