I have come to the conclusion that one cannot have a favourite Temple in Thailand. There are just so many astounding Temples of different styles in so many different places in the country that it is simply impossible to choose a favourite. In Bangkok alone there are a magnitude of impressive temples.
One Temple I have visited numerous times is Wat Arun, also known as the Temple of Dawn, the impressive Temple on the west bank (Thonburi side) of the Chao Phraya river. From Saphan Taksin BTS station take the pleasant riverboat to Tha Thien pier. Tha Thien pier and surroundings is a great experience in its own right....but that can wait for another post...this is about Wat Arun! Once off the river boat you turn right, walk a couple of meters and you will see the turnstile entrance for the ferry across the river to Wat Arun. The crossing as at February 2011 cost 3 baht per person and the trip is 2 minutes or so, including docking time, which seems to require a bit of skill if the river is choppy.
Turn left off the ferry and you will come first to the Ordination Hall with its two giant guardians (Yaksha) standing out front. The main temple complex is off to the left of that, hard to miss really, just look up and you'll figure it out. The striking architectural feature of the complex is the massive Khmer style Prang (tower) which stands at about 76 meters high. It is surrounded by four smaller Prangs. You can climb up steep stairs to two different levels on the main Prang. It is easy going up but, if you suffer vertigo, coming down is a whole different matter. Those steps are really, really steep. There is a handrail - make use of it. The views from up above (though you cannot go anywhere near the top) are spectacular so it is worthwhile making the trip up and suffering gut-wrenching, bowel-loosening, naked, raw, primeval fear on the way down. That gut-wrenching fear will soon be forgotten and the views and satisfaction of having 'conquered' the heights of Wat Arun will make it all worthwhile. (Otherwise just do as I do and descend sitting down on your ass one step at a time like the giggling Japanese university students do - I did the giggling bit too, but the visual effects were not so aesthetically pleasing!)