A disappointing fact first: most of Xinyi's "pool bars" don't exist.
What exists are hotel pools. They host a few summer events, ticketed or by room key, and go dark after September. A bar that keeps its counter permanently beside a pool and lets anyone up — there is exactly one on the Xinyi bar list.
Three tiers: the poolside one, the rooftops, and the places that deliver the same feeling without a pool.
Tier one: poolside, singular
WOOBAR, 10F of Zhongxiao E. Rd Sec. 5 No. 10, 830-plus reviews at 4.3. Bar and pool share the floor; through the glass, water and the lower half of Taipei 101. It is the only Xinyi bar you can point to on the list and say "this one has a pool."
Cocktails run NT$400–600, minimum spend varies by slot, weekends and event nights extra. Whether the deck opens to non-guests on weekdays changes every season — a phone call beats online photos.
The summer pool parties are its famous act: June to September, mostly ticketed, prices and dates per hotel notice. I wouldn't book leave for one — crowded, loud, and the queue for a drink outlasts the drink. Go on an ordinary Thursday instead: pool lit, room under seventy percent full, bartender with time to talk.
Tier two: rooftops, height without water
Barcode, 5F of Songshou Rd No. 22, 920-plus reviews — one of Xinyi's oldest high bars, terrace facing the shopping-district lights. BAR24, same building, unit A19, 130-odd reviews, smaller and quieter; they share an elevator, so check both for seats. Alchemy Bar Taipei, 2F of Xinyi Rd Sec. 5 No. 16-1, 620-plus at 4.4, low floor but the cocktails carry it; next door, Opium Champagne Bar at No. 16-2 1F, nearly 300 reviews, for a slower sparkling-wine evening. Rule of this tier: book. Friday and Saturday after nine, terrace seats are gone; Thursday is the insiders' slot.
Tier three: no elevator, still presentable
Bluntly, pools and height sell a scene. If what you want is a good drink and conversation until midnight, ground level often wins. inari Izakaya, 6F of Songshou Rd No. 9, 220-odd reviews — izakaya-grade drinks list and skewers, NT$600–1,000 a head and you eat better than at the high bars for the same money. Just Exchange Bar in Lane 39 of Keelung Rd Sec. 2, 260-plus at 4.8, runs floating drink prices — good for a group. Ten minutes in, nobody cares whether there's a pool.
Practicalities
Dress code is real here. Hotel and rooftop bars turn away flip-flops and shorts; smart casual is safest. Cards are accepted almost everywhere; a few event covers are cash only.
Don't drive. Mall parking at NT$60–100 an hour is one thing; drinking and driving is another. MRT Taipei City Hall sits at Zhongxiao E. Rd Sec. 5 No. 2, under five minutes from WOOBAR, last train around midnight; after that, cab or designated driver. For the full high-bar circuit, see the Taipei rooftop bars guide; for somewhere quieter, the Dunhua North room in Taipei hotel bars. Xinyi's night isn't only on the tenth floor.