I see the point about Nazca Lines, to bad. But to your other point I have an idea about the Gate. So, you could make the Great Wall's +100% Great general emergence and No barbarians entering borders expire at Explosives, as in reality it's defensive capabilities would later become useless, and it certainly didn't keep out barbarians in the Industrial Era

(Taiping and Boxer Rebellions). You could also make it provide gold after it goes obsolete to represent profits from tourism (If that's possible). You could then give the Brandenburg Gate it's respectable bonus
This is my idea
Brandenburg Gate
Unlocks at Nationalism
Cost: 1100 Hammers (+50% Faster Production with Stone)
+8 Culture
+2 Great Artist Points
+100% Great General Emergence Inside Borders or 2 Free Great Generals
Heres the link for some Brandenburg Gate Graphics:
http://forums.civfanatics.com/showthread.php?t=243855
Oh, here's some ideas for the Dome of the Rock
Dome of the Rock
Unlocks at Dogma
Cost: 775 Hammers
+10 Culture
+2 Great Prophet Points
-50% War Weariness
Anyway, if you want any more wonder ideas I have plenty (Big Ben, Burj Khalifa). Also, I know I'm asking quite a bit but it would be advisable to rename the Kremlin to Saint Basil's Cathedral, it a similar story to the Masjid al-Haram mixup.
Also, I have a question for you. Why are the Turks referred to as the "Turkic Empire"? All of the leaders were leaders of the states that would lead to modern Turkey (Alp Arslan of the Seijuk Empire also controlled Turkey). Also, their short name "Turkestan" only refers to modern day Kazakhstan, Uzbekistan, Turkmenistan,etc. Just wondering.