Is Polkadot a layer 1 or 2?

I'm curious about Polkadot's position in the blockchain ecosystem. Could you clarify for me whether Polkadot falls into the category of a layer 1 or layer 2 solution? Layer 1s are typically known as the fundamental blockchain protocols, while layer 2s are built on top of layer 1s to enhance scalability and functionality. Given Polkadot's design and its role in connecting multiple blockchains, I'm having a hard time pinpointing its exact classification. Could you please shed some light on this for me?