The arches of the solar calendar can be seen  on the floor of the square and they refer to the summer solstice  ( Cancer  - 21 June ) which is exactly the first arch next to the well. Then  there is the arch that is about the entrance of the sun into the constellation of Gemini (20 May ) and Leo (23 July); the third arch shows  the one of Taurus ( 20 April ) and that one of Virgo (23 August ).

The line that crosses all the square is the equinox, and the end of the gnomon shade goes through it on 21 March ( the entrance of the sun into the constellation of Aries)  and on 23 September  ( the constellation of Libra ).

The arch which is on the top right of the photo is about the entrance of the sun into the constellation of Scorpio ( 23 October ) and of Pisces (19 February).