Egypt during the 4th Dynasty to see the Pyramids when they were perfect and still painted or back to the time of Ramses II to see Luxor, Karnak and Abu Simbel just when they were completed and the paint still fresh, though the amount of paint still on some of the temples two weeks ago after over 3000 years is very, very impressive and well worth seeing. Alexandria during its prime would be worth a look as would Jerusalem before the fall of the Temple would also be an impressive city to see and though its weathered better then the others, would like to see Angkor Wat just after it was completed.
-Tig