Caution: this site is in construction.  I have not yet visited Massa Martana, so all the information (particularly about logistics) needs to be checked.

If you arrive from Todi by train, you alight at the station at Villa San Faustino, near the site of the way station that developed beside the Via Flaminia in ca. 220 BC.  It was known as the Statio ad Martis or Vicus Martis and was probably named in honour of Mars.  It later became known as Civitas Martana.  From here, you can visit:

1. ✴the catacomb (see the page on Early Christian Civitas Martana);
   

2. ✴Ponte Fonnaia (see the page on Roman Vicus Martis);
   

3. ✴the Abbazia di San Faustino; and
   

4. ✴Santa Maria in Pantano.
   

Civitas Martana was destroyed, probably early in the 6th century, and a new settlement subsequently emerged some 8 km to the north that became Massa Martana (along SS 316).  This is where you arrive if you take the bus from Todi. 

Massa Martana is a walled town: its main gate (1oth century) was incorporated into a larger circuit of walls in 1277:

1. ✴This is the site of the church of San Felice. 
   

2. ✴Santa Maria della Pace is 1 km to the north, along Viale della Pace.  
   

3. ✴It should be possible to walk from Massa Martana to:
   

4. •Santa Illuminata; and
   

5. •the Abbazia di SS Fidenzio e Terenzio, some 3 km to the west (on the Colvalenza - Bastardo road).
   

You will need a car to get to the Abbazia di San Felice di Giano, some 13 km to the north east of Massa Martana.