One of the customs of Hoshana Rabba is to circle the Bima seven times. Generally, the circling of the Bima on Sukkos is only once. On Hoshana Rabbah we do it seven times. The Tur (OC 660) explains that it is done as a commemoration of what occurred in the Beis Hamikdash itself. The Yerushalmi (Sukkah 4:3), cited by the Tur, explains that it was done in the Mikdash to commemorate the capture of the city of Jericho.
Jericho was encircled seven times before it was captured.
But why now – on Sukkos do we make this commemoration?
The Aruch LaNer (Sukkah 45a) explains that Sukkos is the time of Simcha – where we praise and thank Hashem for tremendous acts of kindness that He has performed for us. The greatest kindnesses were done in regard to the land of Eretz Yisroel. It is therefore appropriate for the seven times to occur on Sukkos itself.