Phra That Phu Phek is an exceptional ancient Khmer sanctuary perched on the summit of the Phu Phan Mountain Range, approximately 520 meters above sea level. Constructed during the 11th–12th centuries (16th–17th Buddhist centuries) during the transition between the reigns of King Jayavarman VI and King Suryavarman II, the monument exemplifies the Baphuon architectural style. The structure is built entirely of green and pink sandstone blocks, meticulously fitted together without mortar using ancient dry-masonry techniques. The temple stands on a square base with indented corners (Yat Mum Mai Sip Song), measuring approximately 11 meters on each side. To reach the site, visitors must ascend a steep staircase of 491 steps, symbolizing a spiritual journey toward the celestial abode of the gods.

From a scientific perspective, Phra That Phu Phek serves as a sophisticated "Stone Calendar," recognized as one of the most accurate archaeoastronomical sites in Southeast Asia. The interior houses a sandstone pedestal, often referred to as the "Reclining Vishnu" pedestal, which is perfectly aligned with the true east-west cardinal axis. Ancient architects engineered specific apertures—doors and windows—to capture sunlight during the four major solar events of the year: the vernal and autumnal equinoxes (when day and night are equal), the summer solstice, and the winter solstice. This alignment was not merely symbolic but functioned as a solar observatory to calibrate the Maha Sakarat calendar, determine auspicious dates for royal coronations, and schedule vital agricultural cycles based on seasonal shifts.

Historically and culturally, the site is intertwined with the "Urangkhathat" or "Phra That Phanom Chronicles." Local legend describes a competitive construction between a group of men, led by Phraya Suwannaphingkhan, who built Phra That Phu Phek, and a group of women, led by Princess Narai Cheng Weng, who built Phra That Narai Cheng Weng. The contest stipulated that construction must cease once the "Phek Star" (Venus/The Morning Star) appeared. The women cleverly hoisted a lantern to mimic the star, misleading the men into abandoning their work prematurely. This legend provides a cultural context for the temple's unfinished summit, which remains a flat, squared-off top today. Beyond the ruins, the site also features ancient hydraulic engineering, including a stone-walled dam and reservoirs that channeled mountain water to the plains below, showcasing an advanced integration of religious faith and environmental management.

• From Sakon Nakhon city, take Highway 22 (towards Udon Thani) for approximately 18 kilometers, then turn left onto Highway 2046, passing through Ban Na Hua Bo, and drive up the paved road until you reach the parking area for Wat Phra That Phu Phek.

• The path to the temple is quite steep and involves many steps. It is recommended to be physically prepared, wear comfortable shoes, and bring drinking water.

• The best time to visit is in the early morning or late afternoon when the weather is not too hot, and you can enjoy the sunrise or sunset views.

• There is a viewpoint at the top where you can see a wide panorama of Sakon Nakhon province.