Turkey is an amazing place. The scenery has tremendous variety: deserts, mountains, beaches, fertile plains, forests, you name it. Whether you want to go white-water rafting, sit on a beautiful beach or explore the fascinating moon-like landscapes of Cappadoccia, you'll probably find what you want in Turkey.
When most people think of Greek and Roman monuments, they think of -- surprise! -- Greece and Rome. What they don't usually think of is Turkey, which is a real mistake. The best preserved, most impressive Greek and Roman ruins I have ever seen were not anywhere in Greece or Italy, they were in Turkey. The museums in Turkey, while not usually well documented, are at least usually labelled in English as well as Turkish (and sometimes German). The ruins of Ephesus, the temple of Apollo at Didyma and the omnipresent Lycian tombs -- carved out of sheer rock faces -- were my favorite attractions. Pamukale -- "Cotton Castle" in Turkish -- is all over the postcards, but many people are disappointed by it, as you can no longer swim in the calcium travertines (the volume of tourists was destroying them). I thought it was well worth a day-trip.
With such diverse geography, you can't really describe the weather in all of Turkey at once. The south coast is significantly warmer than the north, and the middle of the country is at an elevation significant enough to give it snow during the winter. In the summer, though, count on some serious HEAT just about everywhere.
Turkey is cheap. REALLY cheap. I left my bike in Greece and took buses around Turkey. I spent an entire month there, including food, accomodation, museum/monument entrance fees, etc., for $600. Youth hostels are virtually nonexistent, because "pensions" (sort of like a B&B without the breakfast: simple double or triple rooms, often with shared bathrooms) are so cheap. A double room will run about $8-10/night for two people. At one point my temporary travel partner and I managed to bargain them down to about $3 per person per night. A good meal is around $3, and a $7-10 meal would have you eating like a king, including wine, desert, or whatever else suited your fancy. (It was certainly possible to pay more, though, if you left your brain at home.) A loaf of bread is about $0.15, and contrary to what I've heard from people who haven't been there, I never got a single stale loaf.
Turkish food and Greek food have a lot in common. The two cultures will argue for eternity over who actually invented what, but the fact is, if you like Greek food, you'll probably like Turkish food, too. Ordering food in Turkey is often very easy, too, since they normally have several dishes sitting out in heating pans, so you just point at whatever looks good and ask how much it is. The one thing you have to be careful of is when they put something on the table that you haven't ordered: ask how much it costs! If they say it's free, then it is. If they give you a price, then say you don't want it (unless, of course, you do want it, and the price is right).
When I was in Greece, all the Greeks warned me that the Turks would steal everything I owned, kill me and throw me in a ditch. They told me that the Turks were unclean, unfriendly people who couldn't be trusted. This is yet another reason why I have no respect whatsoever for the Greeks. The Turks are some of the friendliest, most hospitable people I've ever met. Even if all you can say in Turkish is "A little of that," "How much is it," "I speak very little Turkish" and know your numbers, you are bound to hear them say "Your Turkish is very good!" (It's been a while, but I think it would be something like (phonetically spelled) "Turkche-siniz chok guzel!")
When I told Turks that I had been to Greece, they asked me what I thought of the place. I told them how much I disliked the Greeks, and how rude and inhospitable I found them. Whereas the Greeks told awful lies about the Turks, the Turks actually defended the Greeks. "Surely you must be exaggerating," they would say, "they can't all be that bad." If I heard a Greek say the same thing about the Turks, I would die of shock.
One thing you do have to be aware of is that the Turks are poor. As a result, they are desperate for your tourist dollars, and will say virtually anything to get them. They won't actually put you on a bus going in the wrong direction, but they might tell you that the bus is air conditioned when it isn't, or that it goes all the way to your remote destination, where in reality you have to take a minibus or taxi the last five miles. Just because the carpet salesman says that his carpets are all made using natural dyes (as opposed to synthetic chemical dyes) doesn't mean it's true -- caveat emptor. This kind of lying can be annoying, but it wasn't enough to make me think anything but positive thoughts about the Turks.
A note for women: the Turkish men can be incredibly pushy and can come onto you VERY strongly. I do not think that you are at much risk of actual physical abuse, but the psychological tolls can be high, as (particularly if you are blond, particularly if you are traveling alone) you will be subjected to verbal harassment and strong pick-ups probably every day. I would almost recommend telling them that you are anything BUT American, since they have seen too much American television, and think that every American woman is a complete slut who will go to bed with the first man who asks.
Again, don't believe anything the Greeks tell you about the Turks. I have never seen so many barber shops, shoe-shine boys or manicurists in my life as I saw in Turkey. Being a muslim country (officially secular, but muslim de facto), personal cleanliness is an essential part of the culture. Theoretically, muslims are supposed to pray five times a day, and before they do that, they are supposed to wash their hands, feet and heads. If you are in Turkey for any length of time, you are bound to see men washing up at the many basins which line the streets, particularly around the mosques.
For one reason or another, Turks pour water all over the place. In the middle of the day, they just hose off the streets, or take bottles of water and squirt them on the pavement outside their houses or shops. Another tourist explained to me that this was because the Koran says something about letting water always flow freely, but I don't know if that was accurate or not.
Despite their personal cleanliness, however, you may not find your accomodation as clean as you might like. Check the sheets to make sure they're clean, and don't hesitate to ask that the sheets be changed. I did this once, and the sheets were changed without hesitation or argument. (I still wasn't totally convinced of their cleanliness, so I slept in my sleeping bag.) Public bathrooms can be absolutely disgusting, so I began to actually appreciate the "squat-style" toilets; the only thing that touches the toilet are the soles of your shoes. It's difficult to get used to, but it's MUCH more sanitary than actually sitting down on a dirty seat. Even more so than in Greece, I strongly recommend bringing at least a sleeping sheet in case the linens are not up to your personal standards.
The Turks, like the Greeks, have not yet become accustomed to the pitfalls of "modern living conveniences," such as plastic bottles and disposable packaging. It is not at all uncommon to see people just throw their bottles out the windows of cars or buses, or take the napkin they just used and drop it on the ground as they walk down the street. Recycling is completely unheard of.
The terrain in Turkey ranges from long, wide-open plains to steep mountains and gorges. Do a little research, and you can get just about anything you want out of Turkey.
Riding in a car in Turkey is a white-knuckle experience. Overtaking another vehicle at high speed along blind mountain corners in the opposing lane of traffic is common practice. I did not cycle in Turkey, but I suspect that it would be beautiful, and I imagine that it would feel less dangerous than riding in a car. In just about anywhere other than the big cities, you would probably rarely see cars, and I imagine they would give plenty wide berth. Particularly when I had to deal with the people who would tell me anything to get on their bus (regardless of whether it was true), I really wished I had brought my bike to Turkey. Roads, in general, seemed good, though there were a few spots (Nemrut Dagi and the Chimaera ("Yanartash," or "burning rock") to name a couple) where getting to the main attraction involved going a far distance on VERY rough dirt roads. A mountain bike might be a good idea in Turkey, but I wouldn't call it necessary. You'll be on good Tarmac most of the time.