What is the physical location of Blockchain

Question

 I am new to this technology and I am confused. Please clear my few doubts. Thanks in advance.

Blockchain consists of Blocks but where these blocks are stored, I mean what is the physical location of the blocks. As per my theoretical knowledge blockchain exists in a network but in which network do we need to create our own network or is there any third party those who provide a network for our application.

Suppose I have to develop a land registry application. I need some space somewhere where I can store my blocks. if I store all blocks in my system itself then how it will behave like a decentralised.

Does Ethereum store our blocks in his network?

Blockchain itself is a database but how we can manage the data?