What locations will accept a Capital One card?

Merchants don't choose to accept or reject credit cards based on the issuing bank, but rather on the umbrella organization they're under. Capital One cards are with Visa, so any merchant that accepts Visa will accept the Capital One card.

If you mean what ATMs, then look on the back of the card to see what networks they participate in, and look on the ATM to see if it's part of that network.