The rivalry with Torre:
That between Oca and Torre is the only rivalry between non-neighboring Contrade and is certainly the most heated and felt.
Establishing the reasons for such enmity is not easy: arguments allegedly due to divergent economic interests degenerated giving rise to the first grudges, which then consolidated in a mutual struggle for city supremacy.
The Palio has certainly contributed to cementing the enmity with its thousand events, made of spite and betrayal. Already in the nineteenth century the two Contradas competed on every occasion for the Gobbo Saragiolo (aka Francesco Santini), a mythical jockey, at the time the authentic king of the Piazza: he, indifferent to enmity and faithful to mercenary ethics, won three times for Oca and five times for Torre. Although over the years there have been various attempts to reconcile (the last dating back to the early twentieth century), enmity has never returned. Its irreducibility has meant that the contractors currently feel this rivalry much more than that of a much older one with Onda.
From: Wikipedia, l'enciclopedia libera.