My tips could be summarised as follows:
(1) Keep the child close and engaged in what you are doing. She might not know about `Baroque` but will be interested in the mythical animals on the church`s façade. He might not appreciate the breathtaking view but will notice sheep, lemon trees and poppies.
(2) Be ready and ideally equipped to carry your child, especially when it`s very hot and/or you are walking far. If you want her to go along happily with what you are doing provide something in return. This something is your presence, your back to lean on, your hair to pull and at least some attention.
(3) Allow, encourage and gently guide contact with other children when possible. Provide sweets and fruit to share, remind him of the local word for `thank you` and watch from a distance.
(4) Make sure the physical needs are met: drink especially but also food, shade and toilet.
You might be rewarded with something like our daughter saying, on the last night in Athens hotel, saying: `I don`t want to go home, I want to stay here and see more old things and stones` (and no, I am not making it up!).
Of course there is a limit, and that limit is usually age. I can clearly remember my sister, aged 10 or 11, furiously kicking a millennia-old wall in Mycenae and muttering to herself `Walls and stones and holes! I can dig such a hole with stones myself! Just staring at these stones and holes! It`s boring!`. She was 11 though and you cannot put an 11-year old in a backpack for a sleepy when they get too hot and tired!