It is understood that one should ascend Safa and Marwah to the extent that the Ka'bah becomes visible, then recite supplications, glorifications, and declarations of Allah's greatness. However, nowadays, ascending Safa or Marwah and seeing the Ka'bah from there is not easy; rather, due to the constructions, it has become difficult—except that from certain specific spots on Safa, with effort, it can be seen between the pillars. (For details, see Hadith: 2964)
Source: Sunan Nasa'i: Translation and Benefits by Shaykh Hafiz Muhammad Amin Hafizullah, Page: 2974