The central courtyard is the core of the house governing the entire environment of the house. Courtyards are best ways to improve the functionality of the house as adopted in traditional Indian Culture from centuries. As per Vastu Shastra Courtyards are preferable at the central location of the house i.e. Brahmasthan.
Courtyards as per traditional cultures were the spaces of principal focus of light, ventilation and get together making them holiest and powerful zone of the house. As per Vastu the central space i.e. Brahmasthan should be free from all obstructions to capture all the positive energies that it radiates which is very useful for living beings of the occupants of the house. The circumference up to 1-1.5m of the courtyard should be totally free from any obstructions and built area.
VASTU TO CHARGE COURTYARDS
The best ritual to activate the positive energies of courtyards is to install Kalash in Brahmasthan followed by all spiritual activities. Tulsi plant is preferred in the center as it has all medicinal values and it nullifies the negative energy of the house. Open to sky courtyards brings in all kind of riches and prosperity to occupants.

Sketch of courtyard with Tulsi Vrindavan
SHAPE OF COURTYARD
The best shape of courtyard as per scientific reasoning is square as it is very stable and balanced. Square with all corners straight and at 90 deg is very auspicious and gives stability, balance, health, wealth and happiness to inhabitants. Offsetting grids of square for superstructure with heavy structures on the rear side and semi open spaces towards the courtyard is best practice.

Sketch of square shape offsetting grid for courtyard and superstructure
ACTIVITIES IN COURTYARDS
-Courtyards can be with plants and green vegetation but avoiding thorn plants and other similar plants which would hamper the positive energies of the courtyard.
-Kitchen, toilets, columns, septic tanks, beams, stairs, store room, sleeping and arches, should not be part of courtyard at any cost.
-Columns should not be constructed on Marma Bindu or else it will pull in negative energies in the house.

Sketch showing Marma Bindu location at intersection of diagonals
Thus, open to sky courtyards at Brahmasthan are very impactful in bringing in positive energies in the house preferably with square shape. All positive energy distribution takes place from Brahmasthan to each and every corner of the structure which is utmost necessary for peaceful, wealthy and harmonious relationships amongst the members residing in the house.