Here are top hotels in Sri Lanka that combine strong nightlife (bars, rooftop lounges, clubs, live music) — and which ones offer casino gaming. I’ve noted what each is best for and included sources for the most important facts.

1. City of Dreams Sri Lanka (formerly Cinnamon Life) — Colombo

• Why go: South Asia’s first large integrated resort in Colombo with an international-standard casino operated by Melco, multiple restaurants/bars, a large retail/entertainment precinct and two hotels (Cinnamon Life + the ultra‑luxury NÜWA block). Best choice if you want an on‑site, full-scale casino plus late-night dining and bar options. (melco-resorts.com)
• Practical notes: Casino operations and fit-out were led by Melco; expect a resort-scale nightlife program (bars, lounges, events). Check ID/age rules and the resort’s opening/operating hours before you travel. (ir.melco-resorts.com)

2. Cinnamon Grand Colombo — Colombo

• Why go: One of Colombo’s most lively city hotels with many bars, restaurants and nightlife venues adjacent to shopping/club scenes; convenient central location for Colombo’s evening entertainment. Great for dining, hotel bars and lively evening atmospheres (pool bar, sports bar, cocktail lounges). (No integrated casino on‑site.) (cinnamonhotels.com)
• Practical notes: Busy on weekends; good choice if you want hotel-based bars plus easy access to Colombo nightlife.

3. The Kingsbury Colombo — Colombo

• Why go: Upscale seafront hotel with a prominent rooftop bar/lounge (Sky Lounge) and multiple dining venues; known for live music, cocktails and sunset views — great for rooftop nightlife rather than casino gaming. (thekingsburyhotel.com)
• Practical notes: Rooftop bars often host live music and events; smart-casual dress is typical.

4. Shangri‑La, Colombo — Colombo

• Why go: Luxury hotel with well‑known open‑air bars (e.g., Tiki Bar) and strong cocktail/arrack menus and sundowner culture; good for ocean‑view evening drinks and hotel nightlife. (No casino on‑site.) (Shangri-La.com)

5. Cinnamon Lakeside Colombo — Colombo

• Why go: Large city hotel with several bars and late-night F&B options, often used for events, parties and nightlife gatherings; convenient for city evenings and groups. (No casino on‑site.) (en.wikipedia.org)

6. Mövenpick Colombo / other large Colombo hotels

• Why go: Several international chain hotels in Colombo (Mövenpick, Hilton, Taj, etc.) offer rooftop bars, lounges and regular nightlife programming; pick one near Fort/Galle Face or Kollupitiya for best access to Colombo’s evening scene.
• Practical notes: These hotels focus on bars/rooftop lounges and dining rather than on-site casino gaming. (rofi.lk)

Quick summary — where to stay depending on what you want

• For casino + resort-scale nightlife (gaming, major entertainment, restaurants, retail): City of Dreams Sri Lanka (Cinnamon Life / Nuwa) in Colombo. (melco-resorts.com)
• For rooftop bars, cocktail culture and live music (no casino): The Kingsbury, Shangri‑La, Cinnamon Grand, Mövenpick and other Colombo city hotels. (thekingsburyhotel.com)

Travel & practical tips

• Casino rules: Casinos in Sri Lanka are regulated; expect age/ID requirements and entry fees for foreigners at some venues — always carry passport and verify local entry rules and opening dates/hours before you go. (ir.melco-resorts.com)
• Dress code: Upscale hotel rooftop bars and casinos usually enforce smart‑casual or smart dress — dress accordingly for evening venues. (thekingsburyhotel.com)
• Timing & reservations: Rooftop bars and signature restaurants can fill up on weekends — reserve in advance for sunset slots or weekend nights. (thekingsburyhotel.com)

If you’d like, I can:

• Narrow options by neighborhood (Fort, Galle Face, Kollupitiya) or budget,
• Check current opening status/reservations for a specific hotel and date,
• Suggest nightlife itineraries (bars → club → late-night eats) for a 1‑ or 2‑night stay in Colombo.

Which of those would you like next?