Most day trips from Hoi An go north to Da Nang or west to My Son. Very few riders point their front wheel south, past Tam Ky, to the big green lake in the hills. That is exactly why Phu Ninh Lake is worth knowing: it is the calmest water within a morning’s ride of the Old Town, the islands look like a freshwater cut of Ha Long Bay, and on a weekday you may share the shoreline with a few fishermen and a school group. This guide is written by the Anh Khoa team at 84 Phan Chau Trinh — we rent the bikes, we measured the distance, and we tell you where the lake is lovely and where it is a bit tired.

Is Phu Ninh Lake worth the ride? A quick verdict

Phu Ninh is not a headline sight like the Golden Bridge or My Son. It is a place to slow down: a wide sheet of water, low hills in every direction, islands that change colour as clouds pass, and an eco-resort on the shore with boats, a zipline and a small hot-spring bath house. Whether that is worth two and a half hours of riding depends on who you are.

Our honest take: the lake is at its best as one stop on a southern loop that also takes in the Tam Thanh mural village by the sea and a plate of chicken rice in Tam Ky. As a stand-alone trip it can feel like a long way to sit by a lake.

How far is Phu Ninh Lake from Hoi An, really?

Our old version of this page said “around 45 km”. So do many travel sites. It is wrong. We ran the directions in Google Maps from our shop at 84 Phan Chau Trinh to the gate of the Phu Ninh Lake eco-tourism area and got these numbers:

The “7 km west of Tam Ky” figure you will see everywhere is correct — the lake is 7 km from Tam Ky’s centre, not from Hoi An. From Da Nang, add roughly another half hour; most Vietnamese guides put it at about 70 km. The gate sits at GPS 15.4965, 108.4642 — paste that into Maps rather than typing the name, because several resorts and a mineral-water factory share the words “Phu Ninh”.

So the round trip is about 120 km. On a comfortable petrol scooter that is an easy day. It is also the reason we steer people away from electric scooters for this ride: there is nowhere reliable to charge at the lake, and 120 km plus detours is outside the comfortable range of most rental e-bikes.

The route: coast road vs Highway 1A

There are two sensible ways south. Both end with the same last 7 km from Tam Ky into the hills.

Option A — the coast road (recommended)

Head out past Cua Dai beach and follow the long coastal road Vo Chi Cong south through the dunes of Duy Hai and Binh Minh. Traffic is light, the surface is good and you get glimpses of the sea and the lagoons. At Tam Ky, cut inland through the city and follow the signs west towards Tam Ngoc and the lake. Google Maps picks this as the fastest route, and it is certainly the nicest.

Option B — Highway 1A

Slightly shorter on paper, but you share the lane with container trucks and long-distance buses for most of the way. Useful only if you want to stop in Dien Ban or Thang Binh on the way. We would not choose it on a first ride in Vietnam — read our guide to riding a motorbike in Hoi An before you tackle any national highway.

The last stretch

From Tam Ky the road climbs gently between forest plantations and rice fields.

Why the lake exists: a 1977 dam, not a bay

The “miniature Ha Long” nickname hides the real story. Phu Ninh Lake is man-made. Work began on 29 March 1977, two years after the war, when the Ba Ky river — which used to flow into the Tam Ky river and out to sea — was blocked by a dam between two hills. The reservoir started storing water in 1980 and was officially opened on 27 March 1986.

The purpose was rice, not tourism. According to the Da Nang city portal, the reservoir holds 344 million cubic metres and irrigates around 23,000 hectares of farmland across Tam Ky and the former districts of Nui Thanh, Thang Binh, Que Son, Phu Ninh and part of Duy Xuyen. Before it existed, much of this area grew one crop a year and went hungry in the months before harvest; with steady water it grew two. When it opened it was one of the largest irrigation lakes in Vietnam.

The islands you photograph were never islands. They are the tops of the hills that stood in the Ba Ky valley before the water came.

The name comes from Phu Ninh, a small upland village of the old Tam Ky prefecture that is now a hamlet of Tam Ngoc. Around the water is a protection forest of roughly 23,000 hectares, home to around 148 animal species — 14 of them listed in Vietnam’s Red Book. You will not see much of that wildlife from the resort, but the forest is why the air here feels a few degrees cooler than on the coast.

Sources do disagree on the fine print: the city portal lists the main dam as 620 m long and 40 m high, while other references give 360 m and 36 m. Surface area is quoted anywhere from 34 to 36 km². We give you the rounder numbers and the source, rather than pretend one is certain.

What to do at Phu Ninh Lake

Most of what you can do here is organised through the eco-resort (Google rates it 4.0 from around 900 reviews — pleasant, not polished). Here is what is on offer and what we think of it.

Boat trip around the islands

The signature activity. A covered boat takes you out among the islands — names you will hear include Turtle Island and Monkey Island — for about an hour. It is the easiest way to understand the size of the lake. Go in the morning when the surface is flat and the light is clean.

The 750-metre zipline

A cable runs about 750 m from the shore out over the water to one of the islands. It was promoted as one of the longest in Vietnam when it opened, and it is still a long, fast ride with a view nobody else gets.

Kayaks, SUP and swan boats

Calm, sheltered water makes this a good place for a first go at kayaking. Life jackets are provided and you should wear one — the lake is deep and you should not count on a lifeguard watching the open water.

Camping and a lakeside barbecue

Vietnamese groups love Phu Ninh for overnight camping. The resort rents tents and sells barbecue sets; nights are noticeably cooler than in Hoi An. If you camp, you will probably want to ride back the next morning rather than in the dark.

Just sitting by the water

Honestly, the best hour we spent at Phu Ninh was on a grassy bank with a cold drink. Bring a mat, find a patch of shade and watch the islands.

The hot spring that used to be a geyser

This is the detail that makes Phu Ninh more than a pretty reservoir. Long before the dam, there was a natural hot spring in the Ba Ky valley. According to local records, it pushed water about 3 metres into the air at 60–70°C, at roughly 100 cubic metres a day. When the valley was flooded, the spring ended up under and beside the lake.

Today it is tapped from deep underground and used in two ways. One is the resort’s hot mineral baths — private tubs rather than an open pool. The other is in a bottle: the spring has been bottled and sold for years under the Phu Ninh mineral water name.

Several Vietnamese guides mention boiling eggs in the hottest outlet — ask the staff whether that is possible on the day. The bath prices vary a lot by package (see below), so ask at the counter before you commit.

Prices at Phu Ninh Lake (2025–2026)

We could not find an official price list online, so we compared the two most recent published ones. They do not agree, and we would rather show you both than invent a single “correct” figure. Take cash — card terminals at the lake are not something to count on.

Children under 1 m enter free in both listings. Budget around 350.000–500.000₫ (~$14–20) per person for gate, boat and zipline, plus fuel. Fuel for the whole 120 km round trip on a scooter costs less than a single zipline ride.

Want a room? The resort’s bungalows are listed on booking sites from around 450.000₫ a night (checked September 2026). Tam Ky city, 7 km away, has more choice.

Make a loop: Tam Thanh murals and Tam Ky chicken rice

The lake on its own is a lot of road for a quiet afternoon. Stitch it into a loop and it becomes one of the best full-day rides south of Hoi An.

If you still have energy for another day, the inland villages make a very different kind of ride — see our guides to Loc Yen ancient village in Tien Phuoc and the cool mountain stream at Deo Le.

Best time to go and practical tips

Best months: February to August. The sky is clearest, the water is calm and the boats run every day. April to August is hot on the road but pleasant at the lake, which runs a few degrees cooler than the coast.

Rainy season: September to December is the wet season in central Vietnam and the storm months are September–October. The lake rises, some islands shrink, camping and water sports may be suspended, and the coast road can be windy. Check the forecast the night before and look at our month-by-month Hoi An weather guide.

• Bike: a petrol automatic scooter is ideal. You do not need a big bike for this road.
• Fuel: fill up in Hoi An or Tam Ky. There are no petrol stations inside the lake area.
• Bring: cash, sunscreen, insect repellent, a light rain jacket and swimwear for the hot bath. Our day-trip packing list covers the rest.
• Food: the resort restaurant does lake fish, local chicken and rice dishes. Prices are resort prices; Tam Ky is cheaper.
• Weekdays win: weekends and public holidays bring company groups and music. Tuesday to Thursday is the quietest.
• Swimming: only in the designated pool or roped areas, wearing a life jacket. The lake is deep and cold below the surface.

Phu Ninh Lake FAQ

Distances measured with Google Maps on 24 September 2026 from 84 Phan Chau Trinh, Hoi An to the lake’s eco-tourism area (15.4965, 108.4642). History and reservoir figures from the Da Nang city portal; the hot-spring figures come from local records summarised on Vietnamese Wikipedia. Prices are from two published 2025–2026 listings and may change without notice — please check at the gate. Photos: hoianit.com.