Koh Ker
Briefly the capital of the Khmer empire between 928 and 944 under king Jayavarman IV and his son Hasavarman II, Koh Ker is approximately 100 km northeast of Angkor site. Today, many large statues from Koh Ker are on display at the National Museum in Phnom Penh, the Cambodian capital. The construction of the 30 meter-high pyramid at Koh Ker and sophisticated bas-reliefs on brick at Prasat Kravan.

An Angkorian site in northern Cambodia. My former colleague, Bros, taking pictures using his camera-capable phone.
September 19th, 2006 at 0:52 am
[...] So true, that. The best places in Cambodia are not in Siem Reap, certainly not in Phnom Penh. As the country opens up, places like this get harder and harder to keep secret. But as Karen points out, at least for now, there are still plenty of “gems” out there if you just take the time to look. Posted by DAS Filed in Tourism, Cambodia [...]
September 24th, 2006 at 19:02 pm
I saw Koh Ker in 2003 back when they were demining it; I’d like to go back now that it’s much safer.
http://jinja.apsara.org/blog/2003/05/retracing-steps.htm
The pyramid shape makes it quite unique compared to many monuments in Cambodia. And the small ‘linga prasats’ surrounding it are fascinating.
Andy Brouwer has some extensive notes below:
http://www.btinternet.com/~andy.brouwer/kker.htm