A cave está abaixo do solo, isn’t the basement permanently under the ground? Isn’t está for temporary states?
No. Estar is used in many permanent situations . Death is probably the finest example…Ele está morto!!
@samhitta7, when referring to locations, we commonly use ser, estar and ficar interchangeably. The temporary vs. permanent concept doesn’t apply in this case. In fact, it doesn’t apply in many cases, as @mac.cummings already noted.
A cave está abaixo do solo = A cave é abaixo do solo = A cave fica abaixo do solo (all three would be fine to use)
This thread delves deeper into differences of use between ser and estar, which might be helpful for you: Ser ou Estar ... quando usar?