Athens Marathon - The original. Legend has it that, after the Greek victory at the Battle of Marathon, the messenger Pheidippides ran 26 miles to Athens to break the news - before dropping down dead. Complete tosh, but a nice story. The modern course, adopted for the 2004 Olympics, starts at Marathon and finishes at the Panathenaic stadium.
Maratona di Roma - The race starts at the Colosseum, skirts the Capitoline hill and passes the Circus Maximus before crossing toward the Vatican - and that's all in the first seven miles. The finish is at the Colosseum, too.