How can i do cardio at home without running ? ( i dont have a bike)?

i have a foot injury and im gaining wait. i haven't run in a while. i just wanna run soo bad. i cant join a gym cause i dont have the money right now.

anything i could do without any equipment? there must be somethinggg
i can stand and walk but i just cant run/ stress the foot.
i live in San francisco and i could walk up hills btw.
does that count as cardio? how many calories can you burn walking up hills?
just anything to get my heart going
TIA