Which preposition to use with valdivia

on Occurrences 2%

(Bouvet Island was discovered by the German Deep Sea Discovery ship Valdivia on 25th November 1898.

in Occurrences 1%

Singular to say, when at Valdivia in 1835, I saw some of these men; they were married, and continued to be regarded as a very great acquisition, although a kind of mystery was attached to them.

Which preposition to use with  valdivia