The honest headline is that Sidemen has very little to do and that this is why people come. There is no attraction here. No gate, no ticket, no car park, no swing over a gorge and no queue for a photograph. What the valley has is a landscape you can walk into from your doorstep, a living craft, and a set of day trips that happen to be closer from here than from anywhere else people stay.
Below is everything actually worth your time, sorted by how far you have to go for it.
From your doorstep
Walking the terraces
This is the reason to be here and it is free, unorganised and available from the moment you drop your bag. Paths run between the rice fields from most guesthouse gates. They are earth banks that farmers built to reach their own plots, they are often wet, and in places they are no wider than your foot with a drop on one side.
Half a day gets you down to the Unda at the bottom of the valley and back. There is no marked route and you do not need one: the valley is a bowl, so downhill leads to the river and uphill leads home. Go early. By eleven the sun is unpleasant and there is no shade at all out in the fields.
Trainers, not flip-flops.
The ridge above the village
The high paths on the eastern side of the valley give you the view that ends up in everybody's photographs: terraces stepping down, palms, and Agung filling the sky behind if the morning is clear. The ridge around Bukit Tageh is where most people end up. Sunrise is better than sunset for the mountain; sunset is better for the terraces themselves.
The Unda
The river at the bottom of the valley runs stony, fast and cold between jungle banks. It is a place to sit rather than a place to swim, and the air down there is several degrees cooler than the village, which on a hot afternoon is the whole point. An hour or so down on foot, rather longer coming back up.
Doing nothing
Included here because it is genuinely one of the things people do, and because visitors who have planned a full itinerary tend to abandon it by the second afternoon. The valley is very quiet, the light changes all day, and there is a particular hour around five when everything goes gold and nobody wants to be anywhere else. Bring a book.
An hour of your day
A weaving workshop
Sidemen is one of the last places in Bali where endek and songket are still woven by hand on backstrap looms, and it is a working trade rather than a heritage display. Endek is the everyday ikat cloth. Songket is the heavier one shot with gold or silver thread, worn to temple, and a good piece is weeks of one person's work.
The weaving happens in the front rooms of family compounds along the main road and the lanes off it. You can watch, ask and buy, and the same cloth costs a fraction of what it does in a Seminyak boutique. Ask before photographing somebody at a loom, the same as you would anywhere.
A ceremony, if one is happening
Village temple ceremonies run on the Balinese calendar and have nothing to do with visitors. If one is on while you are here, you are welcome, and it will be the best thing you see in Bali. Sarong and sash, stay at the back, do not walk in front of anybody praying, do not stand higher than an offering, and wait to be waved forward rather than walking in.
Galungan and Kuningan come round every 210 days and are the big one. Every house puts up a penjor, the tall decorated bamboo pole, and the whole valley is in temple dress for a week.
Cooking, and the things the valley makes
Several stays run cooking classes, and they are better here than in the tourist towns for the mundane reason that the ingredients came from within sight of the kitchen. The valley also produces palm sugar, tapped from the flower of the sugar palm before dawn and boiled down in the open, and arak, which is the same sap distilled. Both are made along the lanes and both are worth stopping for. The sugar travels home well. The arak does not.
Half a day, with a car
Gembleng waterfall
Above the valley, a short and steep walk in from the road, ending at a set of shallow tiered pools set into the hillside. What makes it unusual is the aspect: you sit in the water looking out over the terraces rather than up at a cliff. Go in the morning. It is small, and it does not take many people to feel full.
Rafting the Telaga Waja
The river north of the valley, put in near Muncan, running down through gorges and past waterfalls with a drop at the end that everybody photographs. A half day including the driving, run by operators who will collect you from your stay, and the only adrenaline sport within an hour of Sidemen. Wet season means more water and a faster run.
Besakih
The mother temple of Bali, thirty minutes north of the valley on the slope of Agung, and the largest temple complex on the island. Go early. It is on every day-trip itinerary from the south coast, and the difference between eight in the morning and eleven is the difference between a mountain temple and a coach park. Sarong and sash are required and available at the entrance.
A full day, with a car
Tirta Gangga and the east coast
The water palace at Tirta Gangga, with its stepping stones over the carp ponds, is about an hour east. Another half hour gets you to the Amed coast, which is black sand, calm water and the best snorkelling and diving on this side of the island. Half an hour north again, at Tulamben, the Liberty wreck lies close enough in that you swim out to it from the beach rather than taking a boat. Amed and Tulamben together are a full day and a good one.
Climbing Mount Agung
The 3,031 metre volcano the valley sits under. The standard sunrise trek starts around midnight from Besakih or Pasar Agung, takes most of the night, and is genuinely hard: this is a mountain, not a hill walk. It needs a licensed guide, the dry season, and reasonable fitness. Check that the mountain is open before counting on it, because it closes when the volcanology office says so.
For everybody else, Agung is the thing you look at from the valley on a clear morning, which is most of the pleasure at none of the cost.
What is not here
No beach. No nightlife, no bars, no late kitchen. No shopping beyond the weaving and the village shops. No ATM problem, but no cash economy alternative either, so carry some. If a list of these is what makes a place worth visiting to you, the valley will disappoint you and the coast is an hour away.