¶ Construct
Put one (two*) action cube on the hex you would like to build on.
You can build only on a hex with your city or with your peasants, except swamp and water hexes.
Then build one of the following structures.
¶ Building
Pay the goods and coins listed next to 
the structure icon, and place the building token on the selected hex. You can construct up to 4 buildings on one hex for one (two*) action cube, but don't exceed the construction limit.
You can use this building from now on. Production buildings allow you to manufacture the products, military buildings - to recruit the units, and markets - to buy and sell goods.
¶ City
Pay the construction cost, take the city token from your player mat and place it on a hex under your peasant unit. Place the city token on the lowest layer, below all other objects (if any) on that hex. The city token covers a hex completely, changing its terrain type.
Immediately after building a city, take one action cube from the supply on your player mat and put it in your player area. It becomes immediately available for use - you have an extra action cube for this and all the following rounds.
The city can be built at least 1 hex away from other cities. Any city cannot be adjacent.
¶ Castle
Pay the construction cost and place the castle token on the selected hex. Then take one action cube from the supply on your player mat and put it in your player area. It becomes immediately available for use - you have an extra action cube for this and all the following rounds.
The castle increases strength bonus for the garrison, raises your corps size limit, and also gives you the opportunity to recruit elite units.
¶ Wonder
Select a Wonder card from the wonders row before construction begins. Pay the cost of stage I construction indicated on the card, place the Wonder token in your city or on a hex where your peasant is, with the gray side facing up, and put your action cube on it. Once you have accumulated enough resources, place two more action cubes on the Wonder token and pay the cost of stage II construction. Similarly, finish constructing the Wonder (stage III) - pay the cost indicated on the card and use two action cubes again, then turn the Wonder token over with the bright side facing up. It takes five action cubes total in order to build the Wonder.
Action cubes used to build the Wonder are not returned to your player zone at the end of this and all the next rounds, until the round the Wonder is finished. That is, if you have two stages of the Wonder built, you have three action cubes less each round, until you finish the construction.
As the reward for construction of each stage, you immediately gain access to the corresponding ability on the Wonder card.
Once the Wonder is completed, gain 
during the achievement phase each round (including the current one, when the Wonder is finished), unless the Wonder is destroyed.
If the Wonder is destroyed, return its token to your player mat and discard the Wonder card. After this, you may choose a new Wonder card and begin constructing a different Wonder.
¶ Wall / palisade
Pay the construction cost and place a wall token between the hexes along the shared side. You can build up to six wall / palisade sections around a hex with one (two*) action cube, paying the cost of each section.
The wall / palisade can also be built around a city, between a land and a water hex (on the coast), but not between two water hexes.
You can combine the construction of walls and other buildings. For example, by placing an action cube on a hex, you can build a castle on it and several walls around, paying all the necessary resources.
Remember you can perform the maneuver as a free action and move your peasants to the chosen hex right before the construction action.
There are only four places for building on each hex - it is a construction limit. Each production building and military building occupies just one space. Structures like castle and the Wonder occupy all four spaces, while walls / palisades and the city occupy no spaces at all. That is, you can build four buildings or a castle or the Wonder on the hex with the city. No building or Wonder can be built on a hex with a castle, while the wall / palisade or a city can. There is only one place for the construction of a wall or palisade between 2 particular hexes.
On your turn, if you choose construction as your main action, you can build multiple times, placing the action cube(s) on the chosen hex each time.
[*] If there are any action cubes on the hex, thus you have already built here this round, place two action cubes to build on this hex again.
All structures on a player mat are available to build.
¶ Examples
Nadia would like to construct a couple of production buildings in her city, that she has built this round (there is an action cube there).
Therefore, Nadia puts 2 action cubes on that city, pays 3 
+ 3 
+ 15 
, takes 2 forge tokens and 1 artisan yard from her player mat and places them in the city. Now she can produce weapons and fabric this very round.
Mike accumulated enough resources to build a new city. He moves his unit of peasants to the chosen hex, puts 1 action cube and 1 depletion cube there, pays 4 + 4 + 10 and builds the city.
He takes a city token from his player mat and places it on that hex, underneath all the tokens there - namely 2 buildings and a peasant and a swordsman.
Then Mike takes an action cube from the supply on his player mat and puts it in his player zone. Now he can use one extra action cube, but for that he has to pay 2
each round (consumption goes up).
- this will increase his chances to pass a check.
+ 50 
Mike puts one action cube on hex A, pays 2 + 2 + 10 and builds two forges there. Also he pays 2 + 2 to built a wall between hexes A and B, and 2 + 2 - for two sections of palisade between hexes A and C and between A and D.
Since now only Mike's units (and units of his ally) are able to move through the mentioned hexes. If Alex would like to move his army eastward, he has either to destroy the wall first, or bypass it.