Can I join Architecture without NATA?

Yes, you can join architecture courses without attending NATA. 

There are two architecture entrance exam in India at national level. These are NATA (National aptitude test for architecture) and JEE main. Giving any of these two architecture entrance exams, an Architecture aspirant can get a chance to admit into any renowned architecture colleges in India. 

Sometimes students aren't be able to crack either of the JEE Main or NATA exams. So they unfortunately left behind to study architecture. But there are other ways to get admission into B.Arch programme without these entrance exams as well. 

Indeed, there are some state-level and institute-level architecture entrance exams for aspirants so that they can pursue architecture courses. 

Some Institutes which provide B.Arch admissions without a valid JEE Main or NATA score-

1. PES University Bangalore- Aspirants can apply for B. Arch program through the Management quota seats. 
2. Bharati vidyapith college of architecture, Pune- Admission can be done through management quota seats. 
3. BMS college, Bangalore- through management quota seats. 
4. R. V. College of architecture, Bangalore- Aspirants can get direct admission. 
5. Dr. D.Y. Patil college of Architecture, Maharashtra- can get admission with a valid score in JEE main and NATA. 

So yes, aspirants can get admission and persue architecture courses to full fill their dream without giving NATA or JEE main as well. But obviously they need to complete their 10+2 examination first!