After the Samrat Yantra there were two circular buildings and these comprise the Ram Yantra. Each of these structures has a pillar at the centre, the position of its shadow on the floors and walls are used for readings. I believe one building is for the Azimuth (horizontal) readings and the other for Altitude (Vertical) Readings.
Again there are gaps between the floor and the walls to enable observers to take readings. The holes in the walls are to enable wooden planks to be inserted for a user to climb up to make readings and to insert extensions to the markers.
Here you can see the markings on the raised floor of the instrument.
The Misra (Composite) Yantra is the last instrument in the park. In its centre is the Nitata Chakra which shows the meridian at four locations, two in Europe, one in the Pacific Ocean and one in Japan. On either side are parts of a smaller Samrat Yantra. The third section is the Dakshinottara Bhitti Yanra on the east wall which is for obtaining meridian altitudes. The fourth and last element is the Karka Rasi Valaya on the north wall is used to show the entry of the sun in cancer.
Some of the markings on the Misra Yantra. The marble appears to have been engraved after construction and the markings suggest that accuracy of at least 1/2 degree are possible. Indeed Jal Singh was able to update and improve many astronomical tables with his instruments. Whilst he is believed to have been inspired by similar equipment in Samarkaland his four observatories are now unique in the world. We hope to visit the site at Jaipur at some time which has ten instruments many still in working order.