The interesting engineering is not the basemap. It is refusing to let the catalogue rot.

Closures beat cartography

When a venue disappears, every filter that still surfaces it becomes a false positive. Scaffolding goes up. Tickets stop selling. A temporary shutdown turns permanent and nobody updates the old scrape. We treat that as a first-class maintenance loop: drop or correct the record, rebuild, ship. Public copy says 400+; the in-app filters currently hold 413 London entries and 17 day trips. Those numbers only mean anything if dead places leave the set.

Accuracy is the second loop. A useful card answers whether somewhere is open today, what a ticket costs from (or whether entry is free), how long a typical visit runs, the closest Tube or rail stop, plus walking minutes from the entrance. We also carry accessibility notes, short tips, photos, a rating, and badges such as Editor’s pick or Top rated when they apply. Opening hours are pulled from Google Maps data — live records show they were checked on 18 October 2026. Ticket “from” figures appear in euros. Copy on each place is written in-house, in English. None of that stays correct by accident; seasons and price bands move constantly.

Taxonomy is the third loop. Mood chips only help if the labels are strict. Rainy day, with kids, romantic, quirky, thrills, nature escapes, only-in-London, editor’s picks, free entry — if the buckets leak, the phone UI lies. Sorting by top rated, most popular, shortest visit, closest to wherever you centred the map, or gems first depends on the same discipline.

“Real interest,” rebuilt every month

The ranking method is public on the site. We blend Google search trends with signals from activity providers into a score we call real interest, then refresh that blend monthly. Ratings from visitors sit on top, weighted by review volume. Top rated means the uppermost tenth of that combined score.

Popularity alone always collapses to the same landmarks. Monthly trend-plus-booking data catches what people are looking up and booking this season. Hidden gems stay a separate editorial track — thirty-eight of them, not “whatever the algorithm ignored.” On the map that includes Sir John Soane’s Museum (free Holborn townhouse, about ninety people allowed inside at once), Crossness Pumping Station, and the garden at St Dunstan in the East. If one of those loses what made it special, it should exit the gem list rather than linger for search traffic.

Themed routes reuse the same fields: West End stages, football grounds, galleries and museums, landmarks, palaces and castles, parks, bridges, markets, and the Harry Potter London trail (Platform 9¾, Leadenhall Market, House of MinaLima, and so on). Browse hidden gems as a vibe and you get the same open/closed treatment as the Tower of London.

Rebuild the HTML, don’t babysit a CMS

The UI is plain JavaScript and HTML, assembled with Astro, rendered over MapLibre’s vector engine. Streets and buildings come from OpenStreetMap. We self-host Protomaps tiles at tiles.londontouristmap.com; place photos are served from media.londontouristmap.com. Cloudflare Pages serves the site, Layer7 hosts alongside it, and map payloads sit in Cloudflare R2.

Place pages are HTML files regenerated on the server. When rankings shift, hours update, or a venue vanishes, we rebuild and push. Skipping a heavy CMS keeps editors close to what visitors see. Static output loads on a phone browser or a laptop without ceremony. MapLibre keeps rendering under our control rather than a single vendor SDK. R2 is the object store for the data Pages and Layer7 deliver.

Shareable URLs are deliberate: ?place=tower-of-london-2378 opens one attraction; ?vibe=hidden_gems opens a filter; paths like /museums/ open a theme. Desktop shows list and map together; phones go full-map with a sheet that slides up for detail. A locate control helps on foot. Hearts write into a local “My trip” list in the browser — still no login — because the product promise was a map you can use immediately.

Affiliate links for some tickets, tours, hotels, and an eSIM option fund the free surface; the footer discloses that. Hotels appear on their own layer with prices that update live. Curated home blocks cover a top-ten list, gems, and free things to do.

After the catalogue holds still

Next up: additional niche London maps, then a trip-planner module. Niche maps continue the themed routes already live. The planner is meant to turn a saved shortlist into a day you can walk without guesswork.

I never found a holiday-planning map that matched how I actually decide where to go — too many felt decades old, or flooded with junk results. The long game here is fewer wrong pins, fresher hours, and a monthly ranking that still tracks the city people are searching for.

Know London? Wrong hours, a missed gem, or a theme that should exist all help. Start here: https://londontouristmap.com/.