2. In describing a method of transportation:

Andiamo in macchina. (We are going by car.)

Andiamo in autobus. (We are going by bus.)

Viaggiamo in aereo. (We are traveling by plane.)

Viaggiamo in barca. (We are traveling by boat.)

3. In dates—note that nel is the contraction for the prepositional article in il:

Cristoforo Colombo è nato nel 1451. (Christopher Columbus was born in 1451.)

Caravaggio è morto nel 1570. (Caravaggio died in 1570.)