Overview
This guide gives a general overview on considerations for rushing Petra, with Multiplayer in mind, although a good amount of material may apply to both game modes.
Why is the Petra Important?
Petra can be one of the most game-changing wonders in certain circumstances. When you have a city that has a large number of desert hills and oases, building the Petra in that city can improve it greatly.
For comparison’s sake, consider that many players place high value on the Hanging Gardens, which yield +6 food (and +1 culture and a free Garden). In a city with 10 desert hills, the Petra will provide +10 food, +10 hammers (and +1 culture) PLUS a free caravan to that city. In this light, it should be abundantly clear why the Petra is so important (in applicable situations) and why many players will rush it as early as possible and at all costs when they have the appropriate land.
A petra rush can essentially be separated into two parts. The first part concerns what happens from the start of the game (turn 0) until you reach the currency technology. The second part concerns what happens after you reach currency, when you start building Petra.
How to Tech Currency ASAP (Part 1)
The first part of this guide discusses tips on how to get to Currency as quickly as possible from the start of the game so that you can start building Petra before other players.
***************************************** DISCLAIMER ******************************************
First a disclaimer is appropriate. Many players prefer to rush the Great Library when rushing Petra to increase their early game science. In my experience this is often the fastest way to tech Currency. However, I am not going to cover this strategy in this guide. The reason is that if you succeed in a Great Library rush (which I have discussed in a separate guide), then the path from there to Petra is pretty straightforward, and none of the following tips/tricks are really required. Also it should be noted that if you do this strategy, you may not have time to build a second or third city before starting Petra (especially if you want to build Hanging Gardens too), so you may be short on workers, and you may be susceptible to rush from other players.
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When Great Library is out of the picture, it may be less clear how to maximize early game science to tech Currency in the shortest amount of time. This will be addressed here.
Without Great Library, early game science is best achieved through growth and sheer population count, rather than science buildings. A common mistake inexperienced players often make is to build libraries too early (this is done in many situations outside Petra rushes as well). Libraries only provide +1 science per 2 citizens in a city. When your cities are 4 population, for example, a library will only provide 2 extra science. Cities that are very small can easily increase their science by that amount simply by building granaries or receiving food caravans to increase their population. After all, smaller cities grow the fastest, and having extra population means that more production tiles can be worked by the city as well.
In order to build libraries, you must also tech writing. Writing usually costs 40 beakers (on small map, quick pace) with a slight discount depending on how many players have already teched it and encountered you. When your cities are very small, the insignificant science boost you get from building libraries may not pay off the science cost of researching writing by the time you reach currency. For this reason it is usually not optimal to build regular libraries before Petra.
To tech Currency ASAP, you need to focus on growth, and only research techs that are absolutely necessary until you get to Currency. Pottery is a necessary technology because it is required to build granaries, which are needed for growth and to send growth caravans to the Petra-building city. Mining is also an important technology because you will need to build mines on nearby hills in order to maximize production for Petra. You may also need mining to improve luxuries. Bronze Working, however, is not an absolutely necessary tech for building Petra, so I recommend not teching this until after Currency if you are attempting a Petra rush.
You may need some techs that are not on the same path as Currency, such as Calendar, to improve luxury resources. However, you should try to plan ahead and really determine if it is absolutely necessary to improve these resources before Petra. If you have Gold, Silver, Copper and Cotton in your capitol, for example, teching Calendar before Currency is a bad idea, because the three mining resources should be more than enough to keep your happiness positive until you reach Currency. After reaching Currency, then you can tech Calendar immediately afterwards.
On the other hand, if you have 3 calendar luxuries in your capitol, then you will certainly need to tech Calendar before you pursue Currency or any other more advanced tech for that matter.
To maximize growth (and early game science), I further recommend that you tech Pottery first and consider building a Granary BEFORE a shrine. This may be a controversial piece of advice. When players have desert hill starts, they are often tempted to build a shrine right away so that they can get dibs on Desert Folklore. However, building a granary first (especially if you have deer/wheat/banana nearby) can give you a substantial head-start on early game growth, and may allow you to reach Currency 2-3 turns before other Petra contenders. In my opinion, with the appropriate land, building Petra is much more important than adopting a strong faith pantheon such as Desert Folklore. More faith can be acquired later after finishing Petra by building Stonehenge or Hagia Sophia (if they are not taken already). Also, if someone beats you to Desert Folklore, it can serve as consolation by warning you that another player may be competing with you to build Petra, while the other player is completely unaware that you are competing with them for it.
When rushing Petra, it is also important to avoid overexpansion, which can create early happiness issues and kill early growth and science. Take into account how many unique luxuries you have, and what techs you need to improve them. If you have lots of unique luxuries that all require the same tech to improve, then you are in luck, and early over-expansion is not likely to be a problem for you.
Use the time between the start of the game and finishing Currency to build your Petra city to the highest population count that you can (by working growth tiles, sending food caravans to it, etc), and then switch as many tiles as you can over to production ones once Petra building begins.
How to Build Petra ASAP (Part 2)
This section is largely overshadowed by Part 1, which forms the majority of the guide.
While you are teching Currency, in addition to pursuing this technology as fast as you can, you should also be preparing your designated city to build Petra in the quickest time possible once it starts. This means that workers should be sent to the designated city early on so that they can begin building production-based tile improvements (mainly mines), and growth caravans should be sent to the Petra city early on so that it can grow as much as possible by the time you reach Currency, and work as many hills as possible once it begins.
It will also be helpful for you to be mindful of where you settle your Petra city before you begin building it. Many players elect to found their Petra city in a spot that maximizes the number of desert hills in a 3-tile radius, because they want to maximize the long-term benefit they can gain from Petra.. The problem with this strategy is that this position sometimes lies in an area where there are few immediately adjacent hills to work, so the remaining hills must be purchased with gold. Hill tiles are very expensive to gold purchase, and cities’ natural border expansion often annexes hills last. Therefore you should make sure that you place your city in a spot that will give it plenty of production tiles to work when Petra is ready to build, or that you will have enough gold to buy surrounding hills if necessary. This is a major issue that can potentially devastate a Petra rush if there are not enough production tiles for the city to work.
A couple of other miscellaneous considerations are listed below:
- If you have marble as a luxury resource, I don’t recommend teching masonry before currency unless you need to improve it for happiness, despite the wonder production bonus. In this situation I would recommend that you tech currency, then masonry right afterwards and then improve it. Having a 4-5 turn headstart on Petra from teching currency earlier is probably better than a +15% production bonus you will receive on building it.
- Some people like to go Liberty and use a Great Engineer from the Liberty finisher to build the Petra, but Petra will often be built between Turn 50-60 on Quick Pace, whereas it is difficult to finish Liberty by this time. Attempting to build Petra with a Great Engineer is pretty risky and can also cause you to waste an Engineer if you are same turned on it. It can also take several turns to transport the Engineer to the city that you want Petra in if that city is far away from your capitol.
- When going Tradition, you may profit from avoiding the temptation to adopt Landed Elite (+2 food in the capitol) in some situations. When doing a Petra rush, you will probably not have time to adopt all 5 Tradition policies by the time you get to Currency. Since you are rushing Currency and may have skipped luxury improvement techs, you may need to adopt Monarchy for happiness, and Aristocracy is a must for the Wonder production boost. As such, under some circumstances you should consider adopting Landed Elite as your last Tradition Policy after Petra has been built.
Summary
Tech Currency as fast as you can by focusing on early growth, and only researching those techs that are completely necessary, which include Pottery, Mining, and POSSIBLY BUT NOT DEFINITELY other techs needed for luxury improvement.
Avoid founding too many cities early if doing so will cause you to experience happiness problems or force you to stagnate or delay growth to avoid unhappiness.
Concentrate resources such as workers and growth caravans to your Petra city and give it as much support to grow as much as possible until you reach Currency, and make sure it has production-based tiles with tile improvements to work once you reach the technology.
Godspeed