Maastricht

The west wing and crypts of this medieval Romanesque cruciform structure date from the 11th century, and there's evidence of an earlier church and even a pagan place of worship on the site. — Frommer's

Incredible labyrinth of man made caves.  — Atlas Obscura

This attractive 17th-century Gothic church has a soaring if relatively unadorned interior and a 43m limestone tower whose deep red hue was originally achieved with coats of ox blood (now just paint) — Lonely Planet

You must have a stroll down this street: there is a pretty viewing point over a 17C house with a stepped gable and the botanical garden of the Natural History Museum as well as over the other bank of the canal. — Michelin Guide

This "hell's gate", flanked by two round towers is a remnant of the 13C surrounding wall. This is the oldest town gate in the Netherlands. — Michelin Guide

This historical Netherlands fortress still bears the marks of its single siege.  — Atlas Obscura

Exhibitions in this small museum change every few months but even if the current subject doesn't interest you it's worth popping your head inside. — Lonely Planet

This is the largest square in the town...this vast esplanade, bordered by cafés and restaurants with pleasant terraces, is dominated by two churches: St.-Servaasbasiliek and St.-Janskerk. — Michelin Guide