The causeway which leads into Angkor Wat is flanked at exactly paced intervals by pairs of nagas - seven-headed serpents. They represent the serpent beneath which Buddha sheltered. They are, in essence, protective and it is necessary to have as many as can be fitted in.
The causeway conducts one smack into the centre of the whole architectural compostion. All considerations had to be subordinated to that of symbolism and to have built the formal approach from any angle but this would have been to risk throwing the universe, or at least the kingdom, out of balance.