Horizon Astronomy - double sunset - equinox
Horizon Astronomy can use a trick called the
double sunset - this is the easiest way to mark the progression of the sun across the sky. It is harder to see or mark the sun in the middle of a target point or on top of a menhir/megalith due to the size of the sun and its brightness. But if you are observing the very edge of the sun then you can look at the marker stone or formation on the horizon and you will only see a fraction of the sun so you are not blinded.
Horizon Astronomy works because the sun in relation to the earths horizon moves a fraction each day. So one day you have it where you can not see the sun but the next day you can see a fraction of the sun and that marks the appropriate day (solstices, equinox etc)
Dingli Cliffs solar observatory - middle hill - stone circle

Dingli Cliffs astronomy complex - middle hill - ancient landscaping of a hill
The solar/astronomy complex located near Dingli Cliffs Malta are great examples of ancient human landscaping on a large scale. They have been done very purposefully to aide whoever built them to track the sun on its journey across our horizon. They are perhaps one of the oldest examples of horizon astronomy on earth using large scale landscaping.

ancient lanscaping in europe - astronomy observation platfrom
The middle landscaped hill (looks like a Star Destroyer from Star Wars) has building/structure remains on top of it but rests on top of the very long lower part of the hill. Why have these shapes been used and why these specific heights?
At the bottom of the long platform (direction towards the horizon astronomy hill used to mark the solar progression) is a rough stone circle of large megaliths. These may have been moved or may be where they were put.

horizon astronomy - solar equinox observatory and tracking
What happens at the bottom of the platform, level where the stone circle is found is that you can follow the progress of the setting sun against the astronomy hill. Depending on where you stand you will have the sun blocked out, setting between triangle points or even the holy grail of horizon astronomy - the double sunset.
The examples below do not show an actual double sunset but show how the sun appears on the hill top. The large megaliths on the top have been placed precisely and down the north slope of the horizon astronomy hill there are pairs of megaliths and a fallen standing stone.

double sunset solar observatory hill
If you find one of the spots you should be able to get the double sunset that the people who landscaped the area to create this horizon astronomy complex would have used to mark the equinox and solcistes.
Dingli Cliffs solar observatory - middle hill - Star Destroyer platform

landscape and horizon astronomy platform/complex - Malta
The middle hill structure consists of a large platform that has been landscaped for a precise reason. It would appear that the hieght has been calculated to help with solar observations in relation to the landscape and sea horizon around it.

horizon and sperical astronomy - using sea and landscape horizons
One of the more obvious designs for it is the solar observation as the sun goes across the hill between the middle hill and the sea. When standing or sitting on the long platform the sea horizon connects with the sloping edge of the horizon astronomy hill. If you found the spots where the Temple Builders or whoever built this solar observation complex, took their measurements you should see the sun set at various times of the year where the sea level and special marker megaliths on the hill meet.
Although rising and lower sea levels may mean that is not now possible to physically view this but you may be able to calculate it.
Horizon Astronomy - landscape and structures - east hill observatory

spherical and horizon astronomy in the mediterranean (Malta)
The east hill of the Dingli Cliffs solar observation complex is a rounded hill with landscaped flat platforms on its top and sides. These appear to line up with the 2 hills in front and are very likely to also be used to observe the rising sun in the other direction. The sun rises over the cliff tops of
Mtahleb Valley so its movement during the year across the horizon and sky would be perfect from this hill top.

double sunset landscape and structures
This landscaped hill top has a few flat platforms built into the top and side of the hill and from there you get different perspectives of the horizon astronomy hills in front of you. The middle hill in front has a number of stones that suggest it had a structure or megaliths on top of it or around it.

celestial sphere observatory and the equinox
What may have happened is that the ancient solar observatory people used the structures/megaliths to mark the location of the sun on special days or they could have even constructed the astronomy complex so that they made an artificial "double sunset" or a number of them

horizontastronomie observatory and the autumn equinox
at the front and side of the middle hill there is a large megalith that juts out. this may have been a fallen megalith from the structure there or it could have even been placed there to do a "reverse double sunset". basically the edge of the sun would be seen and then the next day no part of the sun would be seen. thus marking the special solar day.

astronomy observatory and marking the equinox

sun dial and autumnal equinox observation
the east hill could also have been used as a sun dial with special megaliths casting shadows that hit certain points or other megaliths on the flat platforms