Is the prayer of the mosque confined to the mosque, and is it obligatory to pray two rak'ahs before the fard (Tahiyyat al-Masjid) when praying in a place other than the mosque, such as an office?

"Tahiyat al-Masjid" (greeting of the mosque) consists of two rak'ahs performed by one who enters, as an act of reverence for the Lord of the mosque. The proof for this is the Prophet's (peace be upon him) saying: "When one of you enters the mosque, let him not sit until he prays two rak'ahs." This can be fulfilled by performing either a fard (obligatory) or a nafl (supererogatory) prayer, and it is specific to the mosque. There are other greetings for other places, such as greeting the Ancient House (Kaaba) by circumambulation for those not from Mecca, greeting the Haram (sacred precinct) by entering into ihram, greeting Mina by stoning the pillars, and greeting Arafat by standing there.