After a prolonged period of spiritual contemplation, at what age did Siddhartha Gautama achieve Nirvana?

The correct answer is 35.

Step-by-Step Explanation:
1. The Great Renunciation: Siddhartha Gautama was born as a prince in Lumbini. At the age of 29, after witnessing the realities of aging, sickness, death, and ascetics (known as the Four Sights), he decided to renounce his worldly life and royal comforts to seek the truth about suffering and existence.
2. Years of Seeking: For six years, Siddhartha wandered the Indo-Gangetic Plain, learning from spiritual teachers and practicing extreme asceticism and fasting. Finding that extreme self-mortification did not lead to ultimate peace, he realized the importance of the "Middle Way"—a balanced approach between indulgence and self-denial.
3. Achieving Nirvana: Siddhartha traveled to Bodh Gaya and sat in deep meditation beneath a sacred fig tree (later known as the Bodhi Tree). Resolving not to rise until he found enlightenment, he engaged in prolonged spiritual contemplation. At the age of 35 (29 years + 6 years of searching), he attained supreme enlightenment or Nirvana, discovering the Four Noble Truths and becoming known as the Buddha ("The Awakened One").