The king Tobit served would have been Sargon II. Shortly before he was killed in battle in 704BCE, Sargon had a new town and palace built twenty kilometres north of Nineveh. This was presumably the palace where Tobit lived within the walls and walked in the gardens.
When Sennacherib succeeded his father in 704/5 BCE, there was an uprising in Judah, which must have put him out of temper with the Jewish people. Sennacherib was noted for his architectural achievements in Nineveh, where he built another new and magnificent palace.
He was murdered by two of his sons in 681BCE (see p.74).