Jantar Mantar is supposedly "abracadabra" in Hindi, and the sites of the same name in Delhi and in Jaipur which we visited certainly created a lot of mystery and alluded to a lot of magic.
In Delhi, the instruments of one of Maharaja Jai Singh II's five observatories around India are red, and magical. Measuring all matter of celestial things, these structures were built in 1725, and are reportedly bang on with accuracy with what they are measuring.
The Jantar Mantar in Jaipur is just next to the City Palace, and was built in 1728, are cream sandstone, and include each of the astrology signs which points line up to the stars.
Like a grown up playground, each instrument, many huge in size, can be walked around, or through, and the wonder is hard not to get caught up in. They are beautiful, and yet a world of mystery.
These structures in Jaipur have been restored and thus, are the best preserved. They have made the World Heritage List. Each one has the description of what it is measuring, and how, even if these are pretty complicated. You can take a guide to walk you through each one, if you have the time.
It's fascinating that such space and massive structures were devoted to the stars and the movement of the sun and moon, in such important places within each city. A complete enchantment of peace and wonder.