Where is disk buffer cache situated

Where is disk buffer cache situated

I have read that The buffer cache interfaces with block devices, and
caches recently used meta-data disk blocks. The Linux kernel reads file
data through the buffer cache, but keeps the data in the page cache for
reuse on future reads.
I know that page cache is situated at main memory. Whether its true with
buffer cache also?
If buffer cache is in main memory, how access is made to it. Whether any
mechanism like paging is used for accessing buffer cache?