Sanskrit is one of the oldest known languages. It is also regarded as a highly scientific language. It is known for its conciseness, and complications.
Many great literary texts, dating milleniums back, have been preserved as it is, in Sanskrit. The reason for this is that the language has maintained its grammar and vocabulary. There have been new words that have been added over time, but the language retains the form - precise and concise. These texts have been passed on word-for-word through the centuries.
A strong formative influence on the Sanskrit language was the grammar of Panini, which regularized and simplified the grammar. The grammatical and linguistic uniformity of some Sanskrit texts comes from editing done after the texts were completed, to bring them into line with Panini's rules. The epics, in particular, bear traces of such editing.
The Vedas are one such great texts and are worshipped and widely read.
Various Upanishads, Puranas and Shastras, were all written in Sanskrit and have been completely intact over time.
Srimad Bhagawad Gita, Sri Vishnu Purana, Sri Bhagawad Purana and so on..
Apart from these, many ancient texts were written in Sanskrit and are available today.
In addition to religious and philosophical texts, the tradition of Kavya court poetry flourished from maybe the sixth to the ninth century. Kavi is hot-house poetry-- it prizes exotic imagery, recherche allusions, and, above all, word play.
Related to the Kavya tradition is the great poet Kalidasa, who is known above all as a poet and dramatist. His poetry shares many characteristics with Kavi, and his plays have a certain similarity of sensibility with Kavya poetry. The Abhijnaanasakuntalam retells a story from the Mahabharata, where the king Dushyanta falls in love with Sakuntala, forgets his love for her by coming in contact with a cursed ring, has a series of adventures and after a long period of time is reunited and re-enamored of Sakuntala.