Regional Rural Banks (RRBs) work at the District level.

Explanation:
Regional Rural Banks (RRBs) are financial institutions that were established with the aim of providing banking services to rural areas and promoting agricultural and rural development. RRBs were set up under the provisions of the Regional Rural Banks Act, 1976.

RRBs are established as a partnership between the Central Government, the State Government, and the sponsoring bank. The sponsoring bank can be a nationalized bank or a public sector bank.

Structure of Regional Rural Banks:
RRBs are organized at multiple levels, including the District level. The structure of RRBs can be summarized as follows:

1. District Level: RRBs operate at the District level and have their headquarters in the respective Districts. Each RRB is assigned a specific area of operation, which usually corresponds to a District or a group of Districts.

2. Branches: RRBs have a network of branches within their operational area. These branches are responsible for providing banking services to the rural population, including farmers, agricultural laborers, and other rural residents.

3. State Level: RRBs are sponsored by a nationalized bank or a public sector bank, which operates at the State level. The sponsoring bank provides financial and managerial support to the RRBs.

4. Central Level: The Central Government, through the Ministry of Finance, provides overall supervision and control over RRBs. The National Bank for Agriculture and Rural Development (NABARD) is responsible for coordinating and regulating the activities of RRBs at the national level.

Conclusion:
In conclusion, Regional Rural Banks (RRBs) work at the District level. They have their headquarters in the respective Districts and operate through a network of branches within their operational area. RRBs play a crucial role in providing banking services to the rural population and promoting agricultural and rural development.