Meet at your hotels lobby and start walking from your hotel to the nearby busy Ason (Ason is the oldest market place in Kathmandu and at the heart of the city) where you can witness the daily lives of the locals, pass along busy streets, shops, squares, ancient temples etc. The tour then leads to the Kathmandu Durbar Square (UNESCO World Heritage Site), the historical and religious location where many temples, palaces, shrines are located. Nearby is the famous Freak Street, the most popular junction during the Hippy era.
Afterwards, continue walk to the Monkey Temple Swoyambhunath (UNESCO World Heritage Site) located atop hill which commands the most spectacular panoramic view of the entire Kathmandu Valley. Swoyambhunath is a Buddhist Stupa and to get to the top, one needs to climb 365 steps. Due to many monkeys residing at its forested area, its popularly also known as Monkey Temple.
Then, walk back to Thamel or alternatively, you can take a taxi from Swoyambhunath to Thamel.